Gas Mileage???

@ AJ/Form /S

I have 3.23 gears... 26.5 tires and Iron Heads ( x Heads ) and as soon as I hook up the VC ..the engine makes this strange sound at 50- 60 mph.. exact the range when I need the VC.... When I accelerate hard... there is no pingnig...
Greetings Juergen