Originally Posted by
OGandtheMTB
Newbie XF owner here, Newbie car guy too. My near showroom condition 36K-mile '05 6Sp NA Coupe is completely stock. I think it's pretty peppy, but I'd like to max out that pep while keeping it aesthetically as stock as possible. I would like to do a tune and throttle body upgrade, as these appear to be the most effective means of squeezing out a few additional horses.
Can someone explain what it is about the stock intake that renders it inferior to an aftermarket CAI?
1) Air flow is a bit more restricted with the stock setup.
2) Stock setup preheats the air more than the aftermarket "cold air intake". (Cooler air is more dense, so when ignition happens, there is more air mass that will expand and push the piston down with more force.)
For the NA, a "cold(er) air intake", throttle body upgrade and tune are about all you can do for more power. You won't get much, you will spend as much as $3000 for maybe 20hp. I"ve heard claims of 50hp but to my knowledge, no one has shown verifiable test results to supports such statements. Improvements to the SRT setup are another matter, I've personally driven modded SRTs that amazed me.