bogging 6.0

Just finished my 6.0 swap into my 86 chevy one ton 4x4. It is hooked to the factory turbo 400 tranny. It is an lq4 with the heads milled .040, comp cam 220/220 .55x .55x on 114ls, truck manifolds in and out, stock tb. The truck fires off and runs great for just a little bit. Then after warms up ever so slightly I lose all throttle response until about 3/4 throttle then it takes off like a rocket. Its like a light switch. On or off. It seems like it comes and goes. As I drove it a little more this evening it seemed like it got better? It also dies on occasion. Do I have a tune problem or a bad componet some where like a tps or something. Wait4me done the tune.

.040 seems like a bit much to mill the heads. Ive never heard of anyone doing over .030 until now.

I got a funny look from my machinist , but he done it anyway.

Im wondering if thats not one of your problems....Did you use shorter pushrods?

You mentioned it fires up nice and runs good until it warms up.
That is a good indication that the O2's are reporting to the pcm incorrectly.
When cold, the engine is in open loop, o2's really don't matter, but as soon as closed loop comes around +-140deg, the o2's report to the pcm and try to trim and add fuel. If the o2's are bad or dead, they report a bad reading, therefore, throwing off the correct amount of fuel to be added or trimmed.

Be sure the o2's are toggling up and down from 50mv to 900mv, if not, they are no good. Replace them with OEM dealership o2's only.

on a side note, that cam really needs a converter and headers.

+1 on the O2 sensors. Good call Bossman.

I'm sure the heads being milled have nothing to do with my problem and, yes, I did put the right length pushrods and shimmed the stands accordingly.

I don't have an actual temp gauge wired up yet(shame on me), but I don't think it could possibly be close to 140 before it starts running crappy but I may be wrong. I have drove it more and I have discovered that it runs fine after its warmed up? I did install a tci saturday night special "truck" converter. Its supposed to be a heavy duty version with an anti-balooning plate, 500 rpm over stock. Didn't want to much stall for its my farm truck and it will tow some. No headers because I like to hook the DD at the local brush pulls when I don't have a sanctioned pull to go to. Still think O2 sensors are culprit?