Engine stalls after warm and let off gas.
 

2001 Cadillac Seville SLS
Codes:
DIM B1324 - Refrigerant overpressure
IPC U1016 - Communication loss
IRC U1016 - Communication loss
MSM B1850 - Service Stability System
TTM U1016 - Communication loss
VTD B3055 - Key not present

Issue:
Car will start and idle good. Once I drive it for awhile and it warms up, it will stall when I let off the gas. I can rev it up and watch the rpm fall straight down to stall. it is intermittent, and I can always restart the car putting my foot on pedal. once I rev car for a couple of seconds it will idle again. Usually happens once car is warm and only letting off of gas pedal suddenly. I have replace Idle Air Sensor and Throttle Position Sensor, Cleaned the throttle bottle flap and ports as well as I could but they seemed clean. I put in a new air filter, and checked/fixed a vacuum leak. what would be my next thing to check? intake boot? MAF Sensor? I am at loss with no troubleshooting codes to help. Any info or suggestions would be greatly appreciated.