i was suffering from exactly the same problem on my AB setup, turned out to be the map sensor (EVEN though the mapsensor was workin correctly and reading the same voltage on a pectel monitor as the new one that we fitted, old one at idle read 0.4vdc, new one read the same yet the rich running was sorted straigh away, one of those that you wouldn't believe unless u saw it with your own eyes, maybe worth trying a differtn 3 bar just to see, i think it may have something to do with the age of them, they might 'work harden' for want of a better term and go lazy.