1992 Chevy Blazer 1992 Blazer starting and running issues

I had a 1991 blazer with a 4.3 carburated motor I took it out and put it in a 1992 4x4 blazer and put a vortec fuel injected intake on it instaed of the carburator.

my problem is that the vehicle will start and run fine for about 20 minutes then when I turn it off it will NOT restart unless I spray starter fluid in the throttle body or let it set for 30 minutes or so.

i have replace the fuel filter, I have checked the fuel pressure at the throttle body and it was fine (i dont remember the numbers right now) I am out of options here I dont know what else to check to find this problem