dont take the iscv out, just pull the plug off it, if the idle drops, then the iscv is being told to open by the ecu, there are a few various reasons this can happen.

to blow the inlet up with air we have a special fitting, which im sure you could make up, take it up to 3 bar.

otherwise if all is well, just get the fuelling/boost checked and set up, and reclaibrate the idle speed via the throttle body screw.