Originally posted by uclaccord
it will affect performance a lot...a 4 cyl is too small for duals...even the accord 6 is stretching it IMO...u'll lose a grip of backpressure, torque, and all of ur low end...u'll have to rev like a civic to get going
Actually you'll gain back pressure. The Y-pipe is what increases back pressure, and the additional metal from a 2nd muffler + piping will cool down the exhaust gasses a little, which will slow it down, and in turn increase back pressure. The 2nd isn't as much of a factor as the 1st...
If you have a V6, you could probably get more gains by ditching the stock dual exhaust, and getting a low-restriction single exhaust. The same applies to I4 Accords...
*I'm kinda quoting this from a previous post in this forum.