I have a westerbeke 4.5bcgb. It has been running fine all year and just now when I went to start it up it was hard to start and when it did start it was idling very low on the verge of stalling. After a while it eventually idles up to almost where it should be. As it’s running I am getting back fires out of the carb every so often. Has anyone. I changed the fuel/water separator and got a lot of air out when removing the old filter. Has anyone had this issue or may know what’s going on? Could it be plugs or more of a fuel issue?