How's the cooling system? No air trapped in the heads causing hot spots? I still think a compression test would help. Maybe that will tell you if there is any carbon buildup with high readings. Have you tried running higher octane fuel to see if it helps? I know that doesn't solve the problem but at least it would tell you if it is a heat/ignition related issue. If it happened when it was stock, that would have to indicate a mechanical cause(i.e internal to the engine, something that has not been changed).
How's the EGR system? Is it all free of blockage or restriction? I understand there are codes that should show up if something is not right but nothing is 100% reliable.
Maybe run a can of seafoam into it and some fuel system treatment as well as fuel system pressure test. Unless that's what you mean by 60psi at idle.

 

the whole top end is new engine makes about 250hp.i havent bothered with compression numbers because it runs awesome cold and operating temp only raises readings anyway.from cold to warm i dont see anything on the scanner that could cause what i am experiencing.i locked the car into open loop and it still does it.this has to be an engineering / heat soak issue with these cars.i wish i had another cpi vehicle to confirm my suspicions.check this out :
S10s love to run cold. - S-10 Forum

 

Interesting. Sounds like a lot of the usual forum 'I know what the problem is' though. I would believe underhood temps more than anything else. I would love to switch to TBI personally. My CPI is a big pile of fail. I'd help you out but I have a bum TPS connector that makes it run like a turd. When it does run, it is pretty good and torques up a bit when it shifts at higher RPMs. I have punched it a few times back when it ran decent but it was cold as you mentioned. Didn't seem to bad except for being a one-wheel-wonder.
The 4.3 is pretty much a work horse that only came in trucks and SUVs. Anyone wanting to go anywhere is going to dump it for a 350.
I'm not sure I completely buy into the heat soak theory though. I understand it to be a 350 with 2 cylinders removed. Unless the 350 had/has the same problems then how can that develop by making the engine smaller? The difference I see is that the 350 has a coolant crossover on the rear of the intake manifold. When I had my 4.3 CPI intake off I don't remember one being there. Maybe it is an issue of coolant distribution causing inconsistant cooling across the heads.
Then again some intakes have it and some don't. Maybe I'm just thinking crazy.

 

lol even with larger tires,factory positive diff,hop shock,clamped leafs,and 100lb in sandbags outback it will still light the tires to hell on a cold engine.its really a great little tow vehicle but why it runs so different warm is beyond me.i am trying not to speculate on what this issue could be but i know everything in the car is perfect and the scanner agrees with me.i cant help it think if these vortec motors are indeed capable of gaining .5second just running cold at the track there must be more to it.doesnt sound like much but a .5 second gain in a 3300lb truck is still roughly 20hp to the rear wheel which is very noticeable in a truck with not much to begin with.question is why

 

LOL are you sure this shouldn't be in the performance area? It's starting to sound more like you're working on eeking extra power in a stock class for the drags or pulling at this point. This is beyond my league now. I'd suggest HPTuners at this point if available for our platform and start working on closed loop tuning. Best of luck to you.