92 300TE . Mechanic says low vacuum pressure

[mizzell]

After trying many things, I took it to a local Mercedes guy (no dealer here). He checked the valve timing and it was right. He checked the compression and it was fine. After a weak of jacking with it he says the vacuum pressure is measuring 10inches and should be 15-17 . BUT he couldnt find any substancial leaks. I have looked and have found only slight leaks that I fixed. Very weak . Hot start is near impossible, while cold is easier but not easy. no power at start but after 40 mph it pulls better.
Is there anything mechanical that could cause low vacuum pressure.
It appears that I made a big mistake thinking I could buy this car and figure it out. My wife is looking forward to having a car again some day soon...hopefully.