I can't find my old post but I can now say... save your money. The only difference I've seen, is a little lower egt at the back cylinders and I won't be able to measure that, to be sure, until I tow again. Our e-test is only for opacity - floorboard it, from an idle, and measure the smoke. The manifold didn't change it. I've timed several WOT runs with 3 different tunes, from 60-80 mph in 6th, the same way I've always timed and recorded the performance of various tunes, and there's no measureable improvement. I'm probably ~450 hp with my higher tunes, maybe a little more. I'm expecting towing egt to be a little lower but I didn't have a problem before. I hope the maniflod helps more for the hot rodders. Craig

 

Till the stock manifold cracks.... I've seen it on 2 trucks now.