Reduce the air pressure in the chrome plated grease nipples and increase the height of the overhead foxtails. That should see you good mate... no no don't thank me... it's my pleasure

 

We have up to 98 octane as pump fuel here in aus.

 

In the UK we have 95 octane as our standard octane level and 98 octane as a "high performance" (read even more expensive!) option.

 

Harley motors are just simply loud with a lot of normal top end noise. From the 2002 Buell X1 Lightning I had to my 2012 Street Bob and every Harley I've ridden in between... As long as it doesn't sound like a bunch of rocks in a can, you're alright. Just make sure you're not lugging the motor, and run no less than 91 octane. You'll always have top end noise from these motors.