Thank you for your comments!
The answer from Malvern:
"The CofC is correct – it has been raised for a STANDARD +4.
This standard +4 is then modified by AeroRacing into the ARp4 specification, as an aftermarket conversion."
So i will drive my new Plus 4 with the necessary understatement ;-)
normaly there is a small sheet with the specifications of the arp4 and how to use the hifi
