Which one would be best to go with after I add my Jethots in 2 weeks? I am wanting to compare the performance gains to the loss in gas milage. If I only loose like 1 MPG with the X over the Y but see a few HP more with the X I would go with the X Pipe. Also Girlfriend has X pipe with 2 12" bullets; I think it is a little too loud for everyday driving on the highway. what muffler would be good for noise control and still allow for decent power gains?

 

it's kindda a bad comparison. the Ypipe is used for a single exhaust and the X pipe is used for a dual exhaust setup.

in theory the dual setup will make more peak, but sometimes at the expense of low end power.

the Ypipe setup makes sufficient power through out the powerband and really doesn't sacrafice much power on top...probably less than 5hp on a mildly modded car.
now if you are talking a 450hp H/C motor the dual setup would be more beneficial.

not knowing your mods, i would say stick with teh Ypipe setup if you have noise concerns. much easier to throw a quieter muffler on and just have a cutout for track/race use, than it is to try to quiet down a true dual setup.

but i hear the sweet thunder mufflers are good. i think they are about 30" long. summit sells some longer bullet style mufflers too. try those. or you could fork over the real $$ and do twin borla XR1 mufflers

 

The gains from the X-pipe will be all in the mid-range. The X-pipe scavenges exaust much better than a Y- system, therefore leading to signifigant increases in torque. There was a guy that posted on LS-1 tech that gined 25 rwtq in the mid by just swapping to the x over the y. Peak power would only be about 5 hp or so, but the mid is were you win races.