Hi Svtmerc,
Since the suspicion is a vacuum leak, have you tried hooking a vacuum gauge to one of the lines and observing vacuum as it runs? If it randomly fluctuates, or doesn't change as a function of RPM, then it's a leak. If it stays steady at a given speed and the vacuum increases as a function of RPM (highest vacuum (most negative psi) at high rpm, lowest vacuum at idle), then it's something else. (Maybe the live data feature of a scan tool has vacuum, but I would check against a mechanical sensor). Just a thought since the spray around everything is really only a one sided test - if something happens due to the spray, then it's confirmed. But if nothing happens, then you just may not of found the right spot, or the leak is small. BTW, when you were spraying around, did you do it at idle, or at something like 3000 RPM? You have a better chance of finding something at higher RPMs.
-Jerry