new engine wont run

[chevy_lifted_4x4]

I have a 91 s10 with a rebuilt motor I just put it aint I cant get it running. My old motor ran perfect but smoked like crazy so I was guessing rings were worn. I got the motor and put my old intake/ tbi back on and when I went to crank it up it would run shortly ok and then when the choke would let off it would die immediatley unless I flooded it to keep it running. I took it to a shop and they told me I had an intake manifold gasket leak, and I'd also have a high idle due to a bent throttle body shaft?-and to replace the throttle body. I towed it back home and swapped out the gasket and used a little silicone to seal it better the 2nd time and tried it again and it ran worse and wouldnt hardley run for a second or two. I thought maybe the intake was warped or cracked so I found a used one on ebay for 20 bucks and tried that, along with a rebuilt throttle body. That didnt work either. It will just turn over and pop and run for a second then die. I left the timing where the shop had it set to the first time and also played with it a little and it made no difference. I talked to a neighbor of mine and he said his dad had one and it had low fuel pressure and was a bad fuel pump. I swapped that out and the filter, and nothing. I talked to another mechanic and he said he ran into a problem similar on a 4.3 where the new motor installed had a cam that was for a carburated truck instead of a throttle body. I dont know what else to try.

[BlazerLT]

Did you set the timing with the black and brown timing wire unattached from the PCM under the glove box?

Sounds like the timing is off a bit seeing when it goes into closed loop it won't run.