Well, even if you could program the Motronic I can't see what would be gained if you are still using the narrow band O2 sensor because as soon as the ECU goes closed loop the AFR will be a lean 14.7:1 which will produce a tendency to surge so what is the point of spending the bucks for a Rexxer?? You want to improve performance then just go wideband O2 sensor LC-1 and be done with it. Costs less as well.
Oh, and if it's an 1150 you are running I wouldn't recommend removing the code plug. You might change from pink CCP to yellow, brown, or maybe green whatever produces best results for you but don't run without one installed.