Headers, downpipe and catback.
 

Hey guys, I've received my shorty header and 2.2 downpipe from ZZP, I am just waiting on my catback. I went with the Gibson exhaust system since it's a bit more cost effective. I already have an airaid intake setup. Now my question is, with this setup after its all put together, will I see a noticeable gain, or just a better throttle response if any? I have a 2008 HHR 2.2L

Honestly, probably not. You MIGHT gain about 10hp with all those mods untuned, which really isn't noticable. Want you want to do now is find someone that can tune your car. That will optimize the mods, fuel/air tables, and, if you're an auto, they can even optimize and firm up your shift points.

A stock 2.2 5spd will be around 125-130whp(A bit less with an auto). The highest whp I've seen from a 2.2 was 187whp, but that was with cams and such. If you are 5spd, I would say with those mods and a tune, you'd probably be around 145whp. Auto would be a bit less.