Volvo penta 4.3 gxi-e

[Shawnn883]

I have a volvo penta 4.3 gxi-e changed pickup tube and the one way valve then the gas line and fuel filters and engine runs just fine but sometimes at idle it will just started running bad can't idle it up backfiring and then after messing with the throttle it will finally straighten out abd be fine the rest of the day then the next day same thing I'll be out for awhile boating and randomly act up then it is fine until the next time could it be a fuel pump? I have cleaned tank with fresh gas as well thia engine is in a 04 regal 1800