GMC Repair: Backfire, gmc yukon, cylinder misfire

Question
99 gmc Yukon 5.7 was driven about 15 mph it died tried to start but want pull the breather off turned it over an I see flames coming out off the carb opening any ideals

Answer
Hi
I would check basics, and perform a tune up, plugs, wires, cap,. rotor.
I would also check and see if any trouble codes (check engine light)
This will help in pin pointing a particular cylinder misfire or area to check.
Possible low fuel pressure can create drive ability issues as you describe, so I would also check fuel pressure, fuel quality.
I personally have never seen a 5.7 jump timing. This would be my LAST approach. Although it
is not impossible, I would check everything else first.
I Hope this helps