Well I installed the the LSJ manifold and down pipe today and here is what I learned first hand.
My HHR is a 2.2 LAP automatic, ok I knew that the LSJ down pipe would not work on the L61 auto without modification, I read somewhere that it would fit the LAP auto without modification. This is not the case, same exact deal, the cat is bigger and touches the sway bar. Will have to address this. Also aside from the o2 bung the LAP and LSJ manifold are visually the same inside the runners and actually the LAP manifold gasket had substantially larger port holes than the LSJ gasket, so I reused it instead.
Also just finished installing a true CAI with Spectre modular components with the filter behind the drivers side fog light hole. Both of these together sound about as loud as I care to have it, even though I would love to go 2 1/2" with the cat-back.
Add in the LE5 tb and I'm pretty sure it's running a little lean, was wanting to hold off on a tune til I supercharged it but I think I might have to go ahead and tune at this point to be on the safe side.

 

Love to see the CAI.