Regarding dipstick ...

From Bosch Fuel Injections & Engine Management (see at
http://www.rb.com/bosch/gfib/gfib.htm) ...

"Another likely cause of trouble ... is air leaks between
the air-flow sensor and the intake valves.  These leaks are
often called "false air" because it is air that has not been
measured by the air-flow sensor.  These (problems) are often
indicated by  hesitation when the engine is cold, or surging
at idle.  If you suspect an air leak, there are many
possible sources ... Check openings to the crankcase, such
as the dipstick, PCV valve, and oil filler cap for air tight
fits.  Check anything downstream of the air-flow sensor ...

I've seen Bosch fuel injected engines (BMW) actually
immediately stop running when the dipstick is pulled.
Remember that modern engines feature "positive crankcase
ventilation," which means the crankcase air is one with the
intake air system, and therefore a leak is a leak.