Onan MicroLite 2.5 LP series L

Okay. Pulled the unit from under the Sprinter today and replaced the PCB (power control board) and the coil assembly. Reinstalled the unit and 12 minutes later it stated it's miss. It took over 20 minutes before it got so bad that it died. As always, it started right back up. I had inspected all the wiring and did not see anything. I decided to eliminate the propane supply system as a possible problem, so took my bar-b-que tank with regulator and hose and hooked it direct to the generator propane supply pipe. This also did not make any difference. I'm was still fairly sure it is spark related, so I borrowed a spark tester from a former co-worker. This is the type that plugs in-line between the spark plug and the plug wire. With this device installed, it is clear to see that when the unit misses, there is no spark. Contacted Cummins and they say there isn't anything in the system that could cause this issue besides the parts I've already replaced.
Does anybody have any other suggestions?
Thanks