Man, this thread is amazing....lots of great info. I'm still debating my proposed change from DL3 to DQX but I'm getting closer. Phil, I don't expect or want an answer until you return from vacation!! I have a 2015 GMC 2500HD SLT manufactured 3/14 DL3 A45 but do NOT have AVF RPO code. Do I need the RZY additional harness? Are the High Ridge mirrors of good quality? Thanks!