Yes, when i went to replace the Air Filter, i noticed how oily it was in and around the Breather?? And only the Breather?? As you say, it was filthy!

Yes the oil has been done to precision and new AirFilter (didn't that make a difference)
Especially when you re-assemble the covers as they should be, not as a found them!!

No more whistle noise on boost back off, no more smoke... just silent acceleration.

Well i thank you for the reassurance. I'll pass it onto the Chop Burner