prop vibration at 80mph

[adem.csl]

hi guys ive recently had my clutch and flywheel changed due to suspected clutch slip and vibration.removal of clutch i found the flywheel was gone but had new clutch.i replaced clutch and flywheel regardless.the problem i have is that ive noticed a vibration/humming noise starts at 80mph to 100mph from between the seats mid tunnel area sounds like prop centre bearing.bearing in mind bmw have only just replaced the diff floor pan and fitted a new diff.what im wondering is could this vibration be due to the butyle tape that sticks the centre bearing to the body?or has anyone had to change the bearing.this noise stops completely at 79.soon as you hit 80 you notice it straight away.