So, outside of the models with the secondary air induction, all eco exhaust manifolds are interchangable, correct? I believe this is true only for FWD models, the Kappa platform ecos have a taper to angle the flange toward the rear of the car for RWD config, but I could be wrong.

Can anyone confirm?

Also, that would mean that a shorty header that bolts up to a cobalt should also bolt to a J - I'm considering the cobalt addiction model. Sorry I dont have a link, but its a simple 4-1 shorty, equal lenght primaries with our three bolt flange for under 300 dollars. The reason I consider this is because I drive the J daily and cannot have days of downtime while I hack and weld one of our available header choices into place. I could have a shop fab a custom downpipe and HF cat later down the road so the whole system is complete.

I wish someone made a 2.5" or 3" downpipe w/ high flow cat

I have ran an LSJ manifold on my car if that helps, bolted right up just needed a 2.5" downpipe, went with a header instead, but it will work, good option if you can get one for real cheap and know someone who can make you a downpipe cheap, a few hp for little $ but a header will probably gain you more that being said no one has ever dynoed a lsj header w 2.5 downpipe vs. a header so no one can say for sure how much better a header would be

Just to be straight, I'm not looking to bolt any other stock eco manifold to my car, i'm looking to expand the aftermarket options to shorty headers that are marketed for other cars w/ FWD or RWD eco powerplants

So would there be a benefit of hooking up a pacesetter LSJ header to an n/a L61. I'm guessing that the larger primaries would mean hp gains would be in the higher RPM's. What I find most appealing bout this header is the collector diameter - its our only option outside of custom that would mate well (read no bottle neck) to a 2.5 or 3" exhaust. I believe that the collector ID is something like 2.8"

I know the supercharged guys are having great results, but what about a cammed n/a?