[77newell]

If after changing the filter it continues to behave badly let us know. It sounds like restricted fuel flow though the response to the "choke" is a bit mystifying as diesels don't have chokes like you used to see on gas engines so if the gen is indeed diesel you are moving something else the responders above have guessed at what you moved but we can't know for sure until you describe its location on the engine.

Now, if a fuel filter fixes the immediate problem you may still have a future problem in waiting. How long since you last changed the filter, if it isn't that long you may have an algae problem and you will at a minimum want to treat the tank with algicide and expect to consume a bunch of filters until the "infection" is gone.