[dean]

I think you are talking about the compressor bypass valve. It has a piston in it and some seals. I the seals are bad you can hear the piston click as you bip the throttle. I did the job myself. I can't remember the exact price of the 2 seals but less than $20 for parts. The labor would take less than 3 hrs if you clean stuff up.
The fast idle thing could be a number of things. So you would need to diagnos what the problem is. That might be worth $400

The other job would be more like $300

Try and do it yourself