At TTD power levels, 2.5" might make 1-2whp more past 7500 rpm. Weight won't matter since it's down low and you're adding ballast anyway.

From what I have seen, there are no significant gains N/A below 180whp or so with 2.5" over 2.25". We have gradually migrated towards putting Borla XR-1 systems with optional muffler (2.25") or RB single tip systems (2.375") on every car in our shop. The RB is prettier and costs a bit less so it tends to be our favorite.

 

Thanks for the info! Unfortunately I cant use an OTS exhaust because of the way my trans tunnel is modified for seat clearance but I will have one built in the suggested fashion