the thumb screw is the high speed adjustment and should be turned out 1 1/4 turns as a starting point, the small needle on the left side is the low speed and should be 3/4 turn starting point that's the low speed adjustment
I was thinking these two screws were high and low, no?
do you have the inner shroud under the top should have rubber isolaters on it sometimes you can put a little silicon tit to raise them up a little to quite things down.
Is there any chance you can show me a pic of the inner? I only have the top cover but the silicone sounds like a good idea, thanks.