We put a XEX on the 468" 3700lb Biscyne with a 2" spacer. At first we had it installed on top of the spacer and it performed like crap. We were then told to install it below the spacer, the car picked up 3 tenths, i think it might be the same with a cloverleaf manifold, but i'm only guessing. Now this car weighs 3700 lbs plus without driver and it runs 6.20's in the 1/8 mi. Don't know what it will run in the qtr. since the change but it ran 10.31 before the change.
Zip.