You tried two sets of headers and didn't dyno them?!?!

 

Unfortunatley,no! The only dyno available is a 45 min drive away and married with 4 kids made it tough to get to. I really felt that the smaller 1"3/4 headers was much better than the larger 1"7/8. better, quicker throttle response at any speed!!

 

Not apples to apples of how your setup would perform but on my 13 5.0 I saw 20hp/20ft lb tq across virtually the entire power band when I added my Kooks L/T with race catted y pipe