Adrian,
I feel we have all done this ,I don't use the stereo any more,unless i'm in traffic.
The cars too quick some times to keep an eye on the rev counter.
6500-6700 is about the max now.keep radio off and practice listening to the pitch of the engine note.
Oh !! and get a nice dump valve and induction kit fitted ,you won't need a stereo.If you havn't got them already.
cheers
paul s