One big reason why people don't custom make their parts is because they don have the time and/or money to invest Ito building parts themselves a CAI is a simple mod, and thats why there are so many custom made ones. But how many people are willing to go out and build a one off custom exhaust for their car? That's why everybody buys off the shelf parts.
Sold - Black 2000 Mustang GT, gone but definitely not forgotten
- Silver 2007 Corvette
Current - DHG 2001 Bullitt