I had a 1969 Dart GTS with a bracket 440 motor that ran 12.23 at 109.6 MPH with a 2.5 inch head pipe out of a set of Hooker 2.0 primary pipe with a 3.5 inch collectors into a set of 2.5 inch old turbo muffs and then into around 40 inches of 2.5 inch pipes exiting in front of the rear tires. I remove the system and the car went 11.39 ET at 117.8 MPH on the next run
My Duster had a 3.0 inch system on it with the same headers going to the rear of the car into a old Magnaflow 14x7x 3.0 in and out muffs mounted at the rear bumper, that car picked up .02 ET and .2 MPH by removing that system in the 1/8 mile
My message is don't go that small if you don't want a bunch of power loss