I'm trying to decide if I should buy a Superchip for $150 or if I should get the I-pipe and the tailpipes replaced with 2.5 inch pipes(pipes might be cheaper). I can't go bigger than 2.5 because the inlet/outlet on the 80 series is 2.5 inches. I don't race my car but I do drive 350 miles a week and I want the mod that will provide the best overall gain.

 

Piping...

 

Could I go with 2.75 inch pipe and slip it over the 2.5 inch inlet/outlet then weld the difference? Would this provide a better gain??