Its rather common for mechanics unfamiliar with the SC, and even Ford, to fail to seal the IC and SC properly. The result can be a loss of power, miss, fast or slow idle. You can check with propane, or unbolt things an reseal them anyway.
Well since the problem is under accelleration I would say that you need to take it back to the clowns that put your plugs and wires in and tell them to re-seat the wires, Or do it yourself I guess.. Also there have been some recent stories of having a broken plug from an install...
If it idles bad then I would say you have a vac leak someplace as well...