The main flaw in the Q-Jet is its relatively small fuel bowl capacity. At wide open throttle, the turbulence of the incoming fuel causes the float to oscillate, along with the fuel flow curve. But if you aren't planning to do a lot of wide open throttle driving, a Q-Jet is a pretty good carb. You have got your cold drivability problem ironed out; I'd stick with your Q-Jet rather than buy a Holley which would also require a new intake manifold.