hey my friend was wondering what size test pipe to get on his r as he heared if you get 2 1/2" u lose to much torque n lose alot of bottom end n then he heared if you get 2 in. pipeing its helps all around. what do yawl know to be true

 

i have 2 1/2 and it works good you don't lose torque. you can really feel it high
end. hope that helps

 

For your boosted B18C5, you'll want 3" exhaust piping.