Problem solved!!

After a couple of false leads, I ruled out any radio or installation issue, as I could reproduce the rpm drop on the test stand with a completely independent set-up.

Along with the replacement pump, Gaspar had sent yet another ECU, but with this one programmed with some custom modified settings. His suspicion was that my engine needed a higher fuel delivery pressure to achieve max rpm, and the pump was being current limited by the nominal M140XBL ECU settings.

So, after consistently being able to reproduce the issue on the test stand, I replaced the original ECU with the new, modified unit. That fixed it!!!

After running for about 2mins at max rpm with no sign of any drop, I replaced the ECU with the original unit and confirmed successfully that the problem returned.

I've now rebuilt my Ultra Flash with all the original parts except the modified ECU and a new Air Trap. Just now waiting on the weather to cooperate to fly it as final confirmation.

Many thanks to Gaspar for excellent customer service - he has gone above and beyond in helping me resolve this issue.

Paul