If you are going to run with the turbo off the car, you'll either have to kludge up the intake to connect the MAF to the throttle body somehow, or leave it unhooked. If you do that I would guess it will idle better if you disconnect the MAF sensor so prompt the ECU into it's limp mode, which is basic speed-density fueling.
Are you going to run it with nothing on the up-pipe at all, open header? :O
Terrible things like this don't happen where I come from. Other terrible things happen instead.
Obligatory 'build thread