i am going to take the QTP off my car, which is for a 3in cutout, do 5.3L's use the same exaust tubing size i.e. 3in?

 

No..someone please correct me if I am wrong, but i think stock tuning is 2.5". It's nothing an exhaust shop can't fix.

 

actually I think the exhaust on a 5.3 is like 2.75-3 inch. 3 inch will work fine on this.

 

The tube right after the Y pipe and right before the mufflers is a 3 inch. I dont have any idea what comes right before the y pipe.

 

thanks guys, i guess i will hold on to my cutout.

 

I think it is 2.75, but 3 inch can easily be welded to it.

 

yeah f-bodys are 2.75 so i use a 3in and it works great

 

The stock size is 2.75 inches. I was going to do a 3" true dual but the exhaust shop said i would lose torque since i have minor mods. So I did a 2.5" true dual on mine so my cutouts are 2.5". both will work though.