Can anyone help? I was thinking of adding a cattman header and a catback exhaust. I was wondering if there is a good amount of power different between just the y-pipe and the complete y-pipe+header piece. If the different is not alot then I was planning to go with ws y-pipe or cm y-pipe and save the rest of that money toward a catback exhaust.

 

On a 4th gen the headers make an additional 5-8 hp over the y-pipe. Versus stock, you can expect a max gain of about 20 hp/tq. The following link is my before/after dyno (stock vs. headers & Y):

Cattman header dynos on my 98

 

If you have the money to get the headers I say go for it. They are on my long list.