hey guys i was wondering if a custom 2 1/2in piping from the main cat back would keep enough backpressure to activate the six ports or is it too big all the way through.

would it be wiser to do a 2 1/2in piping from the cat to the y pipe and into 2 1/4in piping to the mufflers?

this has been bugin me.... thanx

 

let me put it this way... if the piping is 2 1/2inches from the cat back, that size is not too small or too big... the exhaust gases will flow rapidly with not too much extra room, but when it hits the y pipe it splits into two 2 1/2in pipes also... so the exhaust gases will not escape as quickly because of the extra room. but if the 2 pipes are 2 1/4 it will then be tight enough to make the gases escape fast and keep back pressure for the six ports? right? im not quite sure if im correct but im sure all you rotorheads can give me a heads up! thanx
Marc