Alrights heres the scoop......2007 ss s/c non G85 whenever i start my car cold or not fully warm i get this rattling coming from which seems to be the exhaust... its only when its cold and it progressivly get worse as i get on the throttle untill the car is warm other wise its still there when i shift idk NEED sum advice as to what this could be....... and i have a megan drift spec catback with a magna flow muffler thanks

 

Heatshield? Clogged cat?

 

definitely sounds like your cat is in pieces...

 

so heres the deal if its a clogged cat could that be why some days it feels like theres hella pwer and somedays it feels like me moms buick... im joking but it seems some days it runs better than others i have catback exhaust and a injen cai i got the paper in the mail for it and just wondering if there gonna void my warrenty

 

Who knows.. it's really at the dealerships discretion. Just put the stock cat-back on before you take it in. And yeah, that would be why you notice a difference in power from day to day.