I am having the same issue with the E67. I installed a GMPP L96 and it stalls randomly and idles rough consistently when the a/c is engaged. After extensively looking into this (scouring wiring diagrams, parts catalogs and forums). I have not been able to find a solution. I purchased the EZCAN a/c request module for the E38 from RPMextreme.... seems that the E67 uses class 2 serial data and not can or gmlan. I have also been told that the GMPP E67 does not have the hardware to support a/c clutch control. I was hoping to use an ECU from a 2009 Trailblazer SS as it seems the wiring/pinouts are close and so are most of the sensors but I do not see where anyone has a class 2 serial a/c request for the E67. Hoping that someone has a solution. Perhaps code mode to the E67 for discrete a/c request? Class 2 device? Or do I rewire for an e38? Not sure that the express calibration will work with the GMPP L96. Looking forward to some responses.