Another 2.5 inch vs 3.0 inch?

I'm confused. You say a 3.5" collector. The collector is where the exhaust bolts up. Then you say a 3" flange. Do you mean a 3" reducer? I say if you have 3.5" collectors, then run a full 3.5" exhaust. I cannot STAND stepping exhaust down at the collector. That 512 will need every bit of it, IMO.