If it's LS3 , give it better breathing ie OTR cold air and full exhaust. Going too big on exhaust will likely hurt performance. I believe you don't need a 1 7/8 long tubes 4 in 1 and 3 inch system, 2.5 inch with 1 3/4 4 into 1 is more than enough. 3 inch and 1 7/8 probably better for...