Either lack of fuel, belt slip, crank pulley spinning on crank, or needs better tuning.
Just curious, but how does your truck idle with that 114lsa cam?

Jim

 

Check all the above but also you could be getting knock and it pulling the timing. Also could be the intake air temps. There is a table which pulls timing as IAT's go up. This may need to be adjusted. MP112 radix's are known for having very high IAT's when you go to a smaller than stock pulley.

 

KBOBOZ71, why are you not using a meth kit? With that small of a pulley, and those kind of hp/tq numbers, your IAT's have to be really high.
I agree with TurboGibbs about your timing being pulled from the high IAT's.
A meth kit will need to be a neccessary mod for your application. IMO.

Jim