Was getting 32-33 MPG - now I'm getting 22, and the IDLE speed is VERY high?

Sounds to me that it is more of a problem with your M Air Flow sensor, that sensor sends a value based on the air intake which allows your cars ECU to regulate your fuel to air ratios. If it is malfunctioning it could result in your car running rich (dumping more fuel than needed), in turn this would also result in your engine working harder to burn the fuel, hints the high rpms to keep running when idle. Any way its just an avenue to investigate, good luck to ya