Backpressure
#3
Not sure if your state has smog laws but removing the cat is a no-no here in California ! That being said if you do remove your cat for so called performance gains you should have your vehicle tuned (like a Trifecta) for such a mod ! Your vehicle is set for the backpressure / exhaust that is currently on your HHR and just eliminating the cat will make it preform worse !
Best-O-Luck ,
Best-O-Luck ,
#7
To echo the others here, please leave the cat alone, all you're doing is asking for issues and added expense. Things are better engineered than they were in the '70s and 80s, back then pulling the cat off did help some vehicles, but you still had to compensate with carb jetting etc. And as solman98 kindly pointed out, you can be fined and when it comes time to trade or sell your vehicle....guess what you need to put back on.
#9
Go ahead and do it. Then you can spend all your time and money trying to eleminate the check engine lights,not to mention the "reduced engine power " mode. And while you're at it, remove the hood. That's good for another 15 RWHP.