Engine fights starter when starting

This has intemitently happened 3 times now. Acts like an older car with the timing way too far advanced! Have had it a shop twice in the past. Changed plugs, MAS, bought a used ECM & had it reflashed, changed all O2 sensors. Took the last shop 7 hours to get it running. They said spark plugs fouled bad with fuel. Changed O2 sensors again. This happend once two years ago. Once last December. And yesterday it started acting up again! It has been running just fine. I did recently replace the fuel pump and filter. One guy mentioned once there was some type of fuel valve under the intake? When it did get to the point it won't start at all, it was also slightly backfiring thru the throttle body. Yesterday it fought the starter some, but started, also if you jumped on it from an idle it would have a stutter, then it would wind up ok. I'm a old hot rodder. Please dazzle me!