Originally Posted by biz77
Ransom, there would be no reason to switch back to a stock tune for emissions testing. That Cobb downpipe may pose a problem in CO, however. What year is your car? If 05/06, you probably want to swap out that up-pipe as well.
You NEED to ditch the cat in the uppipe if you are going to run more boost. I am pretty sure I read somewhere once about a failed cat on a stock car all up in the turbo before.