which 3'' exhaust do i want?

For reference, I added a 3" TTI X-pipe and Dynomax Ultraflo mufflers to my TTI 1 5/8"-1 3/4" step headers about 1 1/2 years ago. The exhaust ends with the mufflers just in front of the rear end housing and everythiong is coated inside & out. All indications are that it helped, especially after added tuning and removing the 60lbs that it added from elsewhere in the car to get the car back to it's original weight. It wouldn't have stayed on if I didn't think it helped. I believe the X-pipe helps scavanging/velocity. (no cut-outs)

My combo isn't very radical, but it's race-only:

* 360/904 w/2.71 low gear
* Converter flash to 5000+
* Stock heads with 1.88" intake/1.60" exhaust
* .474" lift cam (lots of duration)
* About 10.5-1 compression
* 750 Holley on a dual plane but will experiment with a single plane again soon
* 4.86 gears with 29.5" x 9" Hoosier radial slicks
* 3,530 lbs + or 3,690 lbs + depending on class
* Mid-high 11's in the 1/4 mile.

For a dual-purpose combo, it's usually better to stay a little on the conservative side - exhaust, cam, carb, compression, etc.