I would suggest ot set the idle with a vacuum gauge and adjust for the highest reading.
Look down the throttle bores and see if fuel is coming from the venturi boosters. If it is, then lower fuel level.
You're looking for the throttle plates to be closed so as the plates uncover some of the idle transfer slots. This way will provide a better transition from idle to the main feed system.
As Dennis suggested, check accel pump adjustments. For every minute movement of the throttle, the same should be happening with the fuel pump. This should get you going with cruising, but, for WOT from idle, a dbl pumper is too much.
If you still have an off-idle stumble, increase the squirter size by three numbers. Say you started at 25, install a 28, etc. until it clears up. Some times a swap from the front to rear squirters assists in troubleshooting. There is a hollow screw for the squirter to buy. This helps alot, I don't know why Holley doesn't install it as standard equipment. Holley PN 26-12.
Make sure your friend didn't forget the ball underneath the squirter and the rubber check valve in the fuel bowl for the accel pump.
If you're trying to go from idle to WOT, it won't happen very well with a dbl pumper. TOO much fuel at one time. One can tune engine by ear, and maybe make it work, but, usually a dbl pumper dumps soo much fuel, it overloads. One has to work up the rpm's for a dbl pumper to be good, say start at 2500 rpm.
You're not running a tunnel ram on top are ya?
Everett "OBJECTS IN THE MIRROR DISAPPEAR UPON RAPID ACCELERATION"