I have 1996 Chevy 1500, with the 5.0 Vortec. I got a check engine light that blinks at an idel and goes solid when i accelerate. The engine misses at a idel but smoths out when i accelerate. I am losing coolant but i can not find any leaks on the ground and i have noticed water coming out of the tail pipe but just a little. I have replaced the orange coolant with green and have been running that in it for almost a year. I replaced the water pump not too long ago so i know i am not losing coolant there. I just replaced the cap and rotor and the TPS.

 

May be the intake gasket. Did you run it really hot at any time? If so, then it may be a head gasket.

 

My first impression is head gasket also. Which is a lot better than the alternative, a cracked block.
Sounds like it's time for a compression test.