Mike, Is the gap on the tach reader larger for the 3 than other PS-2 engines, or is it close to an edge?
The tach read can be adjusted by desoldering, but there is a maximum. I find Tach reader spacing to be an issue with some upgrades especially the larger pitmann motor with small flywheels.
I have used Goo and tie wrap to secure a tach reader to the motor vice the holder when the holder gaps the reader to far away from the flywheel.
The only things I can see as issues if this is systematic to these engines is gearing, tach reader gap, or a software issue in the engines profile. G