Still has a stumble/hesitiation

Running problem is where I am weakest. The more aftermmarket and performance is involved the weaker I am. Having said that...I spent the past 3 weeks trying to cure a similar problem with idle rpm changing, and sintermittent stumble. The real puzzle was watching a see thru fuel filter go almost completely dry then fill to about half way in cycles. Replaced everything from the bottom of the fuel tank to the needle and seat. No change.
Problem and cure was so simple I'm still kicking myself for not finding it sooner. Bowl vent wasn't opening. The only way fuel could enter the bowl was for the the air in there to move back into the line and filter.
My point is dont overlook the obvious or simple stuff. Good luck