[Ralph Greene]

Get a tune, and have the tuner turn your cat light off in the computer.

When I took my stock catback off, we cut it just behind the muffler. So I could look into the muffler.

I couldn't believe how small the pipe is coming thru the muffler. I would guess in the 1 3/4" range. A major cork.

Ford saw fit to use a 2 1/2" mid pipe and 2 1/2" catback on the 05's, on an engine making slightly less power than we make. Does that tell you anything?

BTW....3" is way too big for 300 HP....someone above mentioning that. You want exhaust free flowing enough to exhaust, but not so large as to slow down the velocity. Keeping velocity up is important. I have some tuner friends who like to tune around LT's, X pipe, and stock 2 1/4" pipes with good flowing mufflers welded in. They get great street power. And the smaller pipes are quieter than larger pipes...,a lot of the drone from 2 1/2" systems comes from the larger pipes.