p38 4.0 help

can some one please tell me where the iacv valve is and how the rev counter gets it signal as my car seems to be giving eratic readings when you accelerate i have recently put a new crank possition sensor in as i was getting flat spots seems to of helpd but still have flat spots and eratic readings thanks for any help

idle control valve is mounted on the plenum. Tacho signal comes from the engine management ecu and that ecu uses the crank signal.