One brickboarder, I think it may have been Don Foster, took an old oil filler cap and mounted a pressure guage on it to read internal engine prankcase pressure. A tried and true check of pressure has been called the "jiggle test".

On an idling engine you simply loosen the oil filler car as if you were going to remove it but leave it in place. There should be enough negative pressure in the crankcase so that the cap is slightly sucked down and will stay in place. If there is positive pressure in the crankcase, the oil cap will bounce around or "jiggle" on its seat. The presence of the jiggle means either that the flame trap-crankcase vent system is not clear or that there is excessive blow-by.

On the newer B230 engines, the oil filler cap is a lighter design and can jiggle sometimes even with a good crankcase vent system, especially if the engine shakes a bit at idle. The test works fine on my cars with the newer cap, however. You might be able to get an older cap from a friend or a salvage yard. Some make the test by laying their hand over the oil filler opening while the engine idles. You should be able to feel a slight vacuum.

Repairman, if you find you do have positive pressure in the crankcase and you are certain that EVERY part of the flame trap system is open, you may have stuck rings from having poor oil changes in the past. I've been able to loosen stuck rings with an oil additive called Rislone. I use a quart of Rislone in place of a quart of oil at an oil change. This additive is just a concentrated detergent which allows the oil to penetrate and loosen the gunk in stuck rings. It isn't a motor flush which I don't recommend. Another way to do this is to switch to a synthetic oil and let it slowly clean the engine.

There is an additive called Auto RX which get good reviews on the net but I haven't tried it, no need to yet. good luck on fixing your leaks.