If you are using a typical muffler pressure system and the fuel tank/spray bar (jet) relationship and orientation is reasonable then using a check valve in the muffler pressure line typically will cause excessive head pressure at the needle valve inlet and result in an overly sensitive needle causing inconsistant high speed needle settings and various running problems including flame outs due to leaning in flight.

sonnytex are you trying to fix an actual problem, if so what exactly is the problem. If there is no problem I would suggest you not fix it.


John