Click on product names that are links for pictures
Blitz Air Filter: (ZZZZZ)
I first saw this filter when I was browsing through the showroom of Courtesy Nissan. I decided to try a little experiment to see how the flow rate was compared to the K&N type filters. I picked up the Blitz filter and with one hand in the filter blew through the element to see how much I could feel. I repeated this procedure with the K&N filter and I could instantly tell the difference. The Blitz filter allows a lot more air to go through! In the car and on the street, this translates to a quicker response from the engine and quicker spool up from the turbos. There is a downside to this filter and that is that I'm afraid this filter won't stop as many particles as the K&N filters. I'm running the Blitz filter only on certain occassions right now, but am considering using this on a full time basis after further research. I'd say that this is definitely worth the $120ish that Courtesy sells them for.
GReddy Exhaust: (ZZZZZ)
This was the first aftermarket exhaust system that I ever purchased and it was truly worth the $800 that I paid for it from Primespeed. I purchased it from Primespeed for my non turbo car. The finish was excellent, the mufflers were well polished and the pipes were made of aluminized tubing I believe. I never had any problems with this exhaust. It fit on just right as well. The exhaust was actually passed on to Greg Fields' Zweet after I decided to sell the non turbo. The aggresive five inch tips on here had a drawback in that it would draw a lot of attention to the car. Be prepared to answer questions like, "Do you shoot watermelons out of that thing?!?" (New Castle County Police Officer actually asked me that.) Plus every riceboy wanted to race you. However, it did it's job well and sounded great as well. Not too loud, but just a nice deep throaty tone which sounded even better at wide open throttle.
JWT ECU: (ZZZZZ)
For twinturbo 300ZX's, this is a MUST have! Not so much the ECU upgrade, but the boost jets and the ability to up the boost level in your car. You can also try to make your car run richer with other assorted gadgets; however, this is probably the most simple way. All you have to do is unplug the stock ECU, put in the new one and you're all set to go. The main gains is from the boost jets though. If you use the general equation that 1 lb of boost equals 10 hp, you gain about 50 hp when you up the boost 5 pounds. Unfortunately, the gains aren't as high for the naturally aspirated model. Definitely a must have for twinturbo owners. Available directly from JWT for about $600 but you can get a better deal through SGP or Stillen.
JWT/Stillen Filtercharger: (ZZZZZ)
This is definitely another must have. Not just for Z's, but for any car. OK, I take that back, some Volkswagens are actually known to lose power with aftermarket air filters due to them pulling in more hot air than cold air. However, on 300ZX's the response quickens a bit when you put on an aftermarket filter. The most popular are Stillen's or Jim Wolf's. These are roughly the same. The differences in them are that Jim Wolf's does not use a genuine K&N cone filter and the metal base is not polished. Stillen's uses a real K&N filer and the metal base piece is polished making the metal a lot smoother. Both are washable with the special kit that includes cleaner and oil. It is very important to apply plenty of oil on the filter after you have cleaned it as this is what stops water from entering your engine. I don't believe there is much of a difference in gains of one over the other. They have the same effect and the JWT model is usually significantly cheaper at around $100 a piece while Stillen's is usually priced around $140 a piece.
Stillen Headers: (ZZ)
Excellent piece that increases the power on non turbo models as well as gives the car a bit more sound. However, this is not the easiest piece to install as it is very time consuming and involves installing from underneath the car. When I had these installed on my non turbo, it was when I had the engine replaced so the install was included in the cost of replacing the engine. They are currently available for about $450 from Stillen. I could go either way on this piece as I felt a power gain; however, I do not think that the power vs money spent for the piece and labor to install (if I had not been replacing the engine) would be worth it.
Stillen Test Pipes: (ZZZZ)
During my clutch woes of this year, I decided to get a set of test pipes to help with turbolag. I had originally had a set of Primespeed test pipes from a ex-Z owner. However, when I tried to install those pipes, they did not fit properly. The bolt holes were about 1/8" off from where they were supposed to be. I sent them back to the owner and thought about where to go next. I didn't want to spend $500+ on a set of B&B test pipes and chose to go with Stillen. The pipes sell for about $450 from Stillen and are truly worth the money. They reduce turbo lag by a great deal and make your turbo's much more audible. The quality on these pipes were excellent. Very shiny and they have stayed this way. The welds were good as well. However, there was a problem for me. All test pipes are made with AIV connections, which my car does not have. Luckily, Larry at United Auto Sales performed some alterations to make them functional on my car. These are also quite easily DIY so putting them on after a day at the racetrack (ahem) won't be a problem. (They are illegal for use upon public highways and may only be used for off-road reasons.)
Stillen X Pipe Exhaust: (ZZZZZ)
Excellent excellent quality and not that expensive either. Even though my twinturbo came with an aftermarket exhaust system, it was damaged enough that I needed to replace it. When deciding which exhaust to purchase, it came down to the final requirements. I wanted an X pipe instead of an H pipe, and I also wanted all stainless steel. The only two companies that offered these options were B&B and Stillen. I wasn't prepared to shell out over $1000 for an exhaust system and had favored the Stillen from the beginning. The Stillen system lists for approximately $900 and is, in my opinion, the best system out there. While the tip choices aren't as plentiful as B&B's, the finish was absolutely beautiful. Actually, the finish is still very bright and when it does get dirty, a little bit of Simple Green and glass cleaner shines it right up. The weld's were of excellent quality and the exhaust also wasn't as loud as B&B's. I highly recommend this system to anyone trying to decide which exhaust system to purchase.
Superchips ECU Upgrade: (ZZZZ)
Another ECU maker in the great world of automotives. I can't really say much about this company except that it worked for me. The price of their chip upgrade was only slightly lower than JWT's at $400. I felt an increase in my power when I had this in my non turbo Z. However, this is not highly recommended for twinturbo's. If I had to do over again, I probably would go with the Jim Wolf chip on my N/A instead of this one. But again, I can't say anything bad since I was able to run a 14.9 @ 95 MPH with this chip in my car.
Unorthodox Racing Underdrive Pulley (Z)
While many have claimed to have felt an increase from installing this piece, I felt no gains. I purchased this piece for about $150 from SGP Racing. I was not pleased with it at all. I only experienced problems with this piece. The first day that I purchased it, one of the belts that came with it shredded. Luckily, it didn't cause any damage and a new belt was quickly found by my mechanic at the time. Then, before the week had even ended, I started experiencing minor belt squeal, which progressively got worse. I got it back to the shop and they tightened the belts some more. The squeal finally went away, but only by overtightening the belts. By overtightening the belts, this causes premature wear on components such as alternators. This just doesn't seem very appealing to me, so I have chosen not to put the pulley on my twinturbo.