Combo too much for power brakes?

Can someone tell if my combo would be too much for power brakes. When at idle, I have virtually no brakes. I turned up the idle to around 1000 rpm's and it is not so bad, but that seems way to high for an idle setting. Not to mention it almost jumps into gear.

Info you might need: 91 5.0, 73mm MAF Meter, 70mm TB, ported Explorer intake, AFR 165 heads, 1.6 RR's, Comp Cams XE270 HR (512 lift), stock bottom end, built AOD, shorty headers 2.5" exhaust, H-Pipe, Dynomax Super turbo's.

I would not think it was too severe either, but like I said, with the car idling at about 600-700 rpm's, the pedal goes strait to the floor until I pump it a couple of times. The brakes were bled and when the car is off I have a very firm pedal, as well as when the car is at or above about 1100 rpm's.

I would think that if the booster was bad it would be bad at any rpm or vacume. Oh, how do I check how much vacume there is?