This winter im gonna be savin up for a stage 2 kit. Now engine wise i have nomods done. What are some things that i may do to help the performance. ie headers, cat back, intake? When i do install my stage 2 is it better to do it at the gm dealership? or is it ok to do it somewhere else? what are u guys paying for a stage 2 fully installed? I know that GM warrantys the corsa exuast. Now if i bought that dose it need to be installed by them? just a few ?'s so leave me a few answers thx.