I used Dynomax Super Turbos ($49ea at Summit). They have a GREAT sound - not obnoxious at cruise (almost quiet), but they roar when you get into it.
Borla, Bassani, and Magnaflow also make the front in/out configuration.

 

u gota admit it looks pretty sweet coming out the sides.

 

That set-up looks really sweet with the "X" pipe and all, but do have any real performance gains with the side pipes. If not, then why do you put them on other than looks and giving the toll booth guy some smoke?

 

like steeda says there might be some sort of minimal perforamance gains or whatever but i think the main reason is for uniqueness and look.

or for clearance issues like you said before.

 

In the old days, guys used to have them for the cut outs to bypass the mufflers when they raced. They exited out the side, but these go through the muffler first. Not sure I understand the reason other than clearance issues.

 

im thinking about putting sidepipes on my mustang if i ever get to that point

 

And why Daniel?

 

Glen you are very stubborn!

 

I put them on to make guys like you say "Why?"...

Then there's MUCH improved sound, clearance, performance, and replicating the look of 65 Shelby side-exits...[8D]
Why did Ford put them on the 00 Cobra R, Lightning P/U's or Roush Mustangs? All of the above.

 

another reason im facing right now. The rear brake lines on the 65-66's. I dont need to explain anymore do I?