1996 305 to 350 idle surge

I have a 1996 GMC with the Vortec platform. The truck came with a 305 and I just replaced it with a stock 350 with the exception of a Crane Cams Energy extreme 4X4 camshaft. Summit Racing told me this cam is for my application. The truck had a slight stumble in the idle with the 305 software in it. I had the VCM reflashed with the 350 software. The truck ran better but the idle went downhill. When it warms up you place it in gear and sit with the brakes on or with the ebrake on and the truck surges from 500 rpm to 750 rpm. It trys to correct itself and then lopes again. Checked the obvious for a vaccuum leak and bad brake booster. This problem was not present until the reflashing. The idle for the 305 was 700 in gear, and the idle for the 350 is lower at 550 in gear. Anyone use this cam and have the same problems? Would a vacuum canister be an easy way out? Did summit sell me the wrong cam?

Well, if you checked for vacuum leaks, what good is the vacuun canister gonna do? I;m thinking it's the computer still not set up right for a 350.

I though the vacuum canister may assist with increased vacuum. As far as the VCM goes I can't see how it could be set up different asside from a custom calibration for 400 bucks.