So after Eagle got my truck running great I wanted to open the exhaust up a bit. Swapped out the turbo muffler for a free flowing Borla. I talked with him before I did the swap and he said that I would possibly see a rise in the wot shifts. But I got just the reverse.

Before the swap I could run the shifts out to 5200rpm with no issue. Now once it hits 4000rpm it begins to pop and sputter and maxes out at about 4500rpm

Do you guys think this could be something that is in the tune or maybe I need a better ignition?