took my perfect running b16a out of my crashed hf but it my new si now its idling at 4000

 

Make sure the hoses on your intake manifold are still connected. TPS sensor included. Check for CELS.... Not to mention check out your throttle cable (press with your finger to give it some slack and if the idle drops to normal, theres your answer)

 

Check what he said above. Make sure all the vacuum hoses are on and are not leaking. You can pinch or remove them to see if affects anything.

Sounds like the throttle cable is stuck open.