I have a 1991 Gt with the Holley System Max kit. I hooked up a Vac gauge and its reads 10 at a idle, then you punch it goes to 0, then as it climbs back down it goes to 18 and when it returns to idle it goes back to 10. The specs of the cam are: 221/223° duration at .050, .509/.509 in. lift with a 107°. Do I have a Vac leak? or is the low vac at idle due to the cam. Its about 750 rpms at idle. Thanks