1997 Chevy S-10 Startup Problems

Ok here is what is going on. I start the truck cold (been sitting overnight) and it starts and runs fine, I can even rev it in park and no problem whatsoever. The second I put it in gear to pull out of the space and give it gas it will sputter and choke and basically have a seizure like it is trying to die on me. Then all of a sudden it will "catch its breath" and rev real high and run ok. It will rev a bit high for a minute until I come to a stop and then the truck will idle back down to a normal level and run fine for the rest of the day.

Some history.I was having problems with the SES light coming on when accelerating and I was getting the same problem as above but no where near as violent as it has become. My mechanic said it was an egr code. He blocked off the egr totally, said it wasn't really needed, which I understand is ok for some people. He tested the fuel pressure and found it to be only like 10-20 psi. Obviously low. Puts a new fuel pump in and it fixes the psi problem (and my broken gas gauge I have had for live 5 years now, LOL). Runs ok then starts this sputtering crap. So he replaces the MAP and TPS and tunes it. Also replaces all the wires, cap, rotor, plugs, and the o2 sensors (under warranty just as a precaution). It then runs fine and starts fine even cold for two days. Now it is back to the situation I described at the beginning which seems to be getting worse with every cold startup and my mechanic is kind of stumped. But he owns about three s10s so he is adamant about fixing this and getting to the bottom of it.

I am not getting any codes at all right now. The truck is a 1997 S10 4.3L code W with 101,000 miles on it. Any and all help on this would be greatly appreciated by me. My mechanic is checking in alldata today to see if he can find anything, but I know this really has him scratching his head.

Thanks for any help.