If you put the car in neutral, does the vibration go away?
If so, one of the CV joints is likely going bad. It could be a coincidence because I don't see the joints being damaged during the balance shaft job or they were bad but you didn't notice it. FYI, I don't know who said that the rough idle when in drive or reverse with the brake on was a sign that the oil pump needed to be switched over because it's not. That symptom is normally the CV joints.
Who did the balance shaft repalcement? If they didn't tighten the bolts correctly the gears could be walking out of position. You don't have to set the gear backlash - they have a coating that wears away and sets it but you do have to press on the gear so that it's tightened correctly.
It's almost certainly not the fuel filter.
If so, one of the CV joints is likely going bad. It could be a coincidence because I don't see the joints being damaged during the balance shaft job or they were bad but you didn't notice it. FYI, I don't know who said that the rough idle when in drive or reverse with the brake on was a sign that the oil pump needed to be switched over because it's not. That symptom is normally the CV joints.
Who did the balance shaft repalcement? If they didn't tighten the bolts correctly the gears could be walking out of position. You don't have to set the gear backlash - they have a coating that wears away and sets it but you do have to press on the gear so that it's tightened correctly.
It's almost certainly not the fuel filter.