I've seen the IMRC fail, but, I would check the bushings before spending that kind of money.
This is your IMRC
If you follow the cable coming out of the IMRC, underneath your throttle body will be a thin metal arm - roughly 4-5" long. On either end of this arm there are plastic bushings. These plastic bushings become brittle over time and break away. Without the bushings in place the IMRC cannot open the secondary ports on your lower intake manifold (activated around 3500RPM) and then throwing your engine codes.
The bushings are around $10/ea, IMRC $400+