P0506:

"This DTC sets when the PCM detects an engine speed outside of the IAC's range of control."

The PCM has opened the IAC all the way and the idle speed is staying than 100 rpm lower than commanded/desired... it indicates that the IAC not contributing to airmass... IAC passages may be blocked, or IAC may be dying/dead.


P0101:

"The MAF frequency is 50 percent different from the speed density calculation."

The PCM's sanity check of the MAF doesn't agree... either the MAF is really dirty/broken, or the MAF table and/or VE tables are incorrect.