91 chevy silverado 1500 4.3

Cruising at 55 down highway truck died for 2-3 seconds only to refire itself. After doing so for a few days it wouldn’t start at all. Changed fuel pump,fuel filter and all spark plugs. Now runs fine until I shut it off briefly. Then it stalls on me on 3rd,4th and 5th gears. Bucks badly. Is it a fuel issue or something to do with starting it while it’s warm. Also it runs good with the check light ON. Soon as it goes off it starts shutting off and refiring itself when I give it gas.

When the check engine light is on you need to read the error codes out of the computer. You should be able to do that yourself (http://www.obd-codes.com/faq/read-gm-2-digit-obd-codes-free.php). So do that and report what you get.