My brother owns a 2001 f150 XTR 4x4 with a 4.6L. He wanted it as loud as he could get it so he cut the muffler off and put in a piece of pipe. It's LOUD!!! He says it didn't lose any performance but I haven't driven it so I can't say. I myself am super happy with my flowmaster 40 series on my 02 screw.

 

Im thinking of doing that with my catback--just cutting off the SIDO muffler and putting in a Y pipe. Read my thread below "Suggestions on straightpipes/recordings" and read what everyone wrote. and listen to Fordman302's truck WOW!

 

I removed the muffler on my truck. I had a muffler shop make a single to dual y-pipe, then ran 2.25" pipes all the way out the back. It doesn't sound to bad untill you stomp on it, then it's loud!

Mike

 

If you want it loud cut the back two cats off and run straight pipes all the way out the back. It is loud but it sounds real good (just like a harly).That is a real dual exhaust not a Y pipe.