Ok so I'm making a list of things I'm going to get right when I get back from deployment, as far as a header goes, will the GMPP header, for the 2.0 show as much improvement as a pacesetter? Probably going with a corsa sport catback exhaust

My guess on this is probably not

Also is there really difference between 4-2-1 and 4-1 for the header

 

4-2-1 usually gives you better overall performance, but they usually cost more. I'm not a header or exhaust expert, but I would stick to the 4-2-1.