hey guys i just got a mpfi manifold and im wondering what this thing is on the back of the intake its off of a 89 civic Si any help is great thanks again guys

 

Fast Idle Air Control Valve. I think a lot of folks who did MPFI swaps just left it unplugged and it does no harm. Blue wire goes to B2 on the PM6 ECU, . I used a 94 EX manifold on my swap, so I didn't have to worry about it. Nothing is going to B2 on my ECU, and no CEL. Do not confuse this part with the EACV (Electronic Air Control Valve), often called the IACV (Idle Air Control Valve).

 

sweet i grabbed the engine wiring harness so i may wire that up while I'm making my new harness thanks again