[Mike Taylor 3601]

A trick I have learned the hard way is needle and seat sometimes will leak slightly,but they won't run fuel out vent tube like holley,so it's not as obvious,will drop idle a few hundred rpm,and will bog few feet out because runs over. To check this I remove top and hold float pivot down with finger and put fuel pressure to it fuel level will come up shut off float,then watch for about a minute if leaking fuel level will slowly rise,I have got to where I just go ahead and test all of them I work on.

Another thing to look @ is primary butterflies there is idle circuits that have slotted opening the butterflies have to line up with these slots,adjust idle speed screw to line them up,if engine idles too slow then you have to start drilling holes in butterflies to increase idle speed.

You can also slighly choke w/hand if idles has vacc. leak or blocked idle circuits,too lean,etc
Qjets are more sensitive to vacc leaks,low vacc than holley.
I would also check timing could be retarded too much @ idle.
I would just go over basics first which you'll probaly do first anyway
You can find drinking straws that will fit down vent and push metering rods or watch them operate
Mike Taylor 3601