We got done installing my F.C. manifold today but now the car will start and then just die. There is a loud hissing sound and the intake has backfired a couple of times but all of the vac. lines look good. It wont idle at all, and when keeping it at a steady rpm there is a weird gurgling sound in the exhaust. it sounds like its missing when holding the throttle constant and when reving it sounds normal???