Don't know if any of you have access to any Ultra Sonic probes, but this is what I use to find leaks, both Vacuum and pressure. It can also be used to diagnose bad bearing etc.
I have used it several times to find vacuum leaks on different cars including my 78 SC.
It's not cheap, but luckly I use one for my job along with thermography equipment.
Here is a link if anyone is intrested in this type of equipment.
UltraprobeŽ 2000
Scott
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78 911 SC Targa
01 Honda S2000