1987gt40ttop

i have a 5.0 with gt 40 heads, gt-40 upper and lower intakes, 65mm t-body, 24lb injectors, and a lunati .500/.510 cam. With knowing that heres the prob. i have am getting about 9in vacuum at idle. ive checked everywhere for vac leaks with no luck. it holds pretty steady at 9, no surging which makes me think its not a vac leak. i tried pulling different lines and pluggin some off to eliminate things with no luck. i sprayed t-body cleaner around all the intake gaskets, t-body, egr spacer and vacuum lines with no change in idle at all. i tried swapping out vac. guages with the same readings. its making me think that maybe the cam is degreed incorrectly and the valve timing is off. but the car is responsive idles fine and has no valve float or loss of power. it pulls 17-18in at 2000rpm. ive tried every test i can think of, all coming up good. i tried moving the distributor to retard or advance it to see if the reading would change an it stayed basically the same + or - and inch. basically what i guess im asking is could it be that this set up draws that low vacuum at idle or is it more likely the timing is off? i know an aftermarket cam will lower your vac at idle but ive never seen this low. weird thing is i fig this low brakes would be bad but they are working perfectly fine as well