I just put Y8 intake manifold, head, fuel rail and other minor stuff, 93 p28 ecu, on my 92 dx block. Everything works great but the idle. at first it was revving all the time and loud hissing from the black metal box below the intake manifold by the block. I plugged a vaccum line going from the intake manifold top to where it meets the head and the hissing isnt as loud, also it is only revving now in Park and Neutral, also only after the engine has warmed up to operating temperature. There is no check engine light. It drives fine. I have a vafc ready to go in but I want to get the idle fixed 1st. any ideas what's wrong? another site said a air gap in the coolant line and i should bleed the system. Sounds valid since it happens when the car is warm. I wonder if it is a vaccum/emissions problem though?