1995 Blazer Bucking
 

I have a 95 4.3W that is bucking. It does this once it get warm. It does not do it while its cold. Seem to have started after getting gas. Thought it was water in the gas ran dry gas and ran the truck down to almost empty before refilling. No codes have been triggered. Thought it might also be a coil so replaced it. Truck has new injector, egr valve, tuneup, radiator, starter, altenator, waterpump, temp sensor. Its strange with no codes. Any ideas
Thanks