[mcfly94]

Originally Posted by Sox

This dude is on the money.
2.25" is the ducks guts for the 5L, and they absolutely need a balance pipe.
2.5" would work well from the headers and in the mid section, but the tailpiece must be 2.25".
Making the pipe smaller as the gas travels encourages flow.

keep in mind you guys are talking about stock 5l's being the 185 to the 220kw yes? even a 220kw with a mild cam would be best with the 2.25
but alloy head and aftermarket intake, cam, surely begins 2.5 territory