Ok so I got this 85 glht and I'm having a few problems with it. Boost is set at 16-17psi. Nothing too crazy. I go wot and it's good till 5000 or so rpm. It misfires. Dunno why but it does. Kinda sounds like a 2 step. Fuel pressure is good 70psi at that boost level. Cap rotor wires are fine. Egt is between 1400-1450. So plenty of fuel. Shudder wheel seemed to be fine. Can a failing hep cause that without throwing codes?how about cam timing?