I have test pipes already installed in my car but i want to do headers should i buy shorty headers and keep the test pipes or sell the test pipes and buy longtubes, do you get the same power from either setup? thanks

 

The G37's OEM exhaust manifolds are headers. These are them:



There are aftermarket headers available, but I believe you're splitting hairs here... unless you go long-tube and get your car tuned.

 

Long-tube should help your torque a small bit but will likely do nothing for max HP.