Had to pull the plenum to change a leaking fuel rail oring got everything back back together car started up idled fine.Then i noticed i left the brake booster vac line off so pluged it back in then car died.so tryed starting the car again started up but will not hold idle so disconnected the vac line to the brake booster and it held and idle? the vac lines look to be all good but going to look over all them tommorow? is there anything else that can be causing this? the car is 1991 Z28, 5.0, 5 speed