Trying to get to the bottom of my missing bhp and i have had a vacuum pressure test (mercury) done on my car.
Apparantly it should be around 15-18% but mine is less than 5% !!!
Can any one shed any light for me - it should be a 190 engine lol
surely someone has had a similar problem/issue ?
Have you done a cylinder ‘leak down’ test? It should be less than 10%… one of mine was leaking 30% which meant about 20bhp lost!
New rings sorted it.
Is that any use?
Pete. 
Sorry not to be able to offer any really worthwhile advice, but I certainly had a few idling/rough running problems with mine which may (or may not?) have been at least partially due to loss of vacuum. In my case, I discovered that one of the small t-piece connectors on the thin bore vacuum pipe had a crack in it (to the extent that it was almost snapped!). I replaced it, but unfortuantely also changed the TPS, OAT Sensor and Brown Temp Sender at the same time. My car ran perfectly afterwards but I cannot conclusively state what the main original problem was!
Anyway, just wanted to say that, as good as this site is, you will generally get a far better reply on SELOC - a simple case of membership size … Try posting there too if you haven’t already.