On CAIs- I had one in my 87, and I believe it made a difference. It was a BBK chrome piece, fenderwell mount, my car was a 302, Ecam, gt40P heads with valve job, GT40 intake, roller rockers, and lots of other goodies. Good for about 300 RWHP. Now, I had a factory 91 GT MAF in there at first. IIRC, those are the same diameter as the inlet tubing, and it was choking the shyt out of my motor like you wouldn't believe. I added a larger Gianelli MAF (which I actually had good luck with, believe it or not, they're known for sucking ass), and my CAI, and the car woke up bigtime. On my 04, I noticed that nice little WOT sound, and a slightly better throttle response. Now, I am no longer running a chrome one. I have the black plastic Roush one now. I will say, the old chrome one on the 87 would get very hot to touch. I don't, however, believe it affected the air inside too much, because that stuff was moving way fast. Overall heatsoak will bog any car, but stick a piece of plastic and a piece of metal in a 250* oven for a while, and they both end up at that heat. Our underhoods are all ovens (which is why I am getting a heat extractor hood). I will say that adding the bigger filter, and being able to mount it inside the fender where it is sniffing cooler, non-engine bay air, probably helped keep inlet temps down a bit more, and it's doing it more effectively than the factory air silencer did. Simply removing the silencer and adding a K+N is an improvement, but by no means better than a fenderwell mount, because it is now open to the hot engine bay air. Also, look inside the factory tubing. Better yet, run some water through. Look at all the turbulance caused by the ridges molded into it. Now repeat with any CAI. It's smoother. At higher RPM, which means higher air draw rate through the CAI, less turbulence means more air, which means more power. So, basically, a fenderwell mount CAI is worth the time of day. It's no earth shattering mod, like gears, suspension, or a blower, but it is worth something. Now, for the guy who doesn't give a rat's ass what the underhood looks like, and he's staying bolt-on or stock, then it's a waste. For a guy who wants better looks, a tad better performance, or plans to build to a level at which the stock air tract is going to be a problem, then yes, it's worth it. We spend far more on spoilers that we all know don't do jack **** for our cars except look good. Imagine a nice chromed out motor with a stock inlet tubing.
