3" tti

After running open TTI 1 5/8"-1 3/4" headers with collectors on my 360 Stock class Dart Sport for a couple of years, I switched to a 3" TTI X-pipe ending with mufflers at the rear end housing and picked up .05 - .10 in ET! I had to remove 70lbs that the exhaust system added from elsewhere in the car to get the weight the same and did minor jet changes.
Your results may vary, but it worked for my combo.