Starting Issues

I have installed the ignitech modules on my Rotax 912 and all of my starting issues went away, however new problems appeared. I did a good run-up after installing the modules and everything looked good. When taking off about 50 ft off the ground I aborted takeoff because of something that sounded like backfire and noticeable power loss. I taxied back and did another run up this time starting at 4000 and gradually bringing the power up one mag at a time. One module is able to go full power while the other afterfires out of the exhaust around 4500. 

For the past few weeks I have been trying to figure out the problem which is difficult because it is intermettent. Sometimes both modules will work sometimes one of them won't. I have switched spark plugs, installed new ignition cable and caps. I have tried every single scheme between ignitech module connectors and 6-pin connector to try and trace the problem. I looked at the programming in each module and they match each other and they also look correct regarding rotax specs.

When I install known good rotax modules I get no afterfire on either one at any RPM. Any ideas? Is my luck bad enough to have had three failed rotax modules and now a brand new failed ignitech module?