Hello, I have a 98 with a 5.9 from a 99. The truck originally had the 3.9. My wife bought it for me site unseen, the guy told her that it needed a tuneup. When I got around to it, I found out it was a lot more than that. I will start with what I have done.
New plugs,wires, cap, rotor, pickup coil, coil, injectors, iac Crank sensor, compression and fuel pressure check And the timing checked by my local dealer.
It starts And will idols rough, it will detonate in the exhaust. If I disconnect the iac the idol smooths out but still it will detonate. The kicker is if I disconnect the #2 fuel injector, the detonation stops. it still idols smooth but won't go above 30. Any suggestions would help.

 

Sounds to me like you got a bad injector, not uncommon for new parts to be bad these days.

 

Swapped injector with no change. I'm at a loss. Going to pull valve cover to make sure exhaust valve is closing.