I was wondering which is the best exhaust header for my 2.2 HHR.
I read on this forum that the 2.0SS or 2.4 exhaust manifold would be the best exhaust manifold for my 2.2.

With my experience already owned an Alero 2.2 ecotec, I replaced the exhaust manifold with a header and DP (don't recall the make), high flow cat and a magnaflow muffler ...... and then sold the car, the buyer wanted to have the original muffler put back, once I replace the muffler with the original, I notice a major increase in power. (kept the header, DP and high flow cat).

Can some one confirm that the 2.0SS & 2.4 exhaust manifold will increase the exhaust flow and is better then my original manifold, I won't replace the cat nor the muffler for now.

Your experience and knowledge will help