I just rebuilt the head on my 01 Prelude and I just got it running. It automaticly revs itself from 1500- 4300rpm at idle. I sprayed some carb cleaner by all the vacuum lines looking for leaks and found none until I went by where the IM meets the head. It appears my IM gasket didnt seal in that spot.... I also got a code for both Throttle Position sensor and Vehicle speed sensor. Is is possible the codes are from the leak or is it more likely a TPS issue?

 

Your TPS might need adjusting. You'll have to check its voltage

Your leak should be causeing that wierd reving reving. If you don't feel like pulling it all apart, degrease, and alcohol swab the area. Let dry, and than use high heat resistant silicone sealent.
(I had a slight IM leak after I pulled it so I pussied out and used grey silicone sealent (good for 700 I think) and its been fine for 2 years. No leak at all, and doesn't brake down from heat (resulting in smells and falling off).

Vss could be an indipendent problem. Personally I don't know of the other two (throttle posistion sensor, intake manifold leak) issues resulting in a vss failure. If your 5th gen is like mine your VSS is ontop of your tranny I think. Maybe check the wires/connector/contactor. You might have missed something simple.