Sounds like the gyro servo is in the correct 'sense'.

My hunch is that the faster servo, possibly combined w/
the new gyro tape is letting you see a mis-tuned engine.

However, mounting tape does make a difference. You can
certainly try a different tape, thats easy and you might want to
try adjusting the engine mixture too.

IMO, the little shelf behind the mainmast is a better location.