I have a 2007 HHR with the 2.4L and a 5 speed. I can get a Walker cat(54579) for about 150, but the listing says it's for an automatic and no one knows if it will fit the manual. i called a Chevy dealer and found out that the rest of the exhaust system is the same for both, including the exhaust manifold, but they list a different p/n for each. they only thing the parts guy cold guess is that the bends in the middle are different to clear the auto tranny. has anyone tackled this before?

 

I ran into this issue when I had to replace the cat on my 06, 2.2 5speed. The shape is the same for all. What you need to look at is, where are your O2's are located.

One model had the upstream O2 in the manifold, and the other is in the pipe. Mine was in the manifold. But I found a cat with a bung for the upsream O2 pipe hole and installed that. I got it shipped off ebay for about $130 if I remember correctly.

Here are the 2 side by side:


Good part is, you can change it with it just up on ramps. I did like the flex part on the original better than the mesh the new one had.

 

If you buy one WITH the bung it can be plugged if not needed. Opposite not so.

IIRC, the manual has the bung on the manifold. So you could get either model.