[leegrady]

If it runs better with the two barrel it means the secondaries on the Q-Jet were coming on too soon.

There is an adjustment for the spring on the secondary plates that open, and raise the secondary metering rods. These are the butterfly plates right on the top of the carb. (not the throttle plates). Increase tension on the spring so your secondaries open later. The carb will act like a two barrel until higher in the rpm range, with much better response. Esp. if your Q-Jet came off some other vehicle.

Note: the primary metering rods on the Q-Jet are numbered, as are the jets. In this way they can be mixed and matched to dial the carb. in richer or leaner. I have no reason to believe you have any problem with this, just thought maybe it might interest some readers.