Chris,
    I'm still getting the RPM drop out, exactly as you describe.  I did install a Capacitor and resistor, then (if I remember correctly) deleted the resistor.  This was at Tracy's direction.   There was no real change.  Sometimes I also have numbers and characters appear erratically and just as fast, they disappear.  Usually it's on the EGT display.    Due to the optical nature of the optical tach, depending how light reflects off it, it will sometimes read 2 or 3 times the actual prop RPM.   So, how does these issues effect my flying with the EM-2.  They doesn't.  I really, really  like the EM-2.  It is GREAT  to have a real-time mixture display and to be able to control the mixture.  Instant feedback!  It's great to have all the info you need on one display.  It is ever greater to feel comfortable enough with the EC-2 and the engine to take my eyes off the EM-2 and just fly with my eyes outside the airplane.  I find that when I feel comfortable, I only use the optical tach and just fly regular RV prop RPMs.  Now all these things add to the uncertainty of the first few hours in the air and add to the work load.  If you decide to fly, do your best to ignore this stuff, fly the airplane, watch your temps and watch and control the mixture.
    Additionally, a couple of times during most flights my EM-2 trouble light will blink on.  I'll scan the display, looking for a blinking parameter, but won't find one.  I'll press the #4 button and fly merrily on.  Is it a noise issue?  Could be, probably, who knows. Only heavy duty experienced EE types.  It is my understanding that being in a plastic airplane, noise issues can be worse.
    I would like to have all these minor issues solved, but if they are not, it's still good.  Maybe it's like looking for the perfect woman.  You aren't going to find her.  Good enough is still really good.
    Like many issues I have had, if I wait long enough, someone else will have the same issue and will have a partial solution and then it is worked out online for the benefit of us all.  This has not happened so far.  Maybe this is the time.  I'm open to suggestions and am willing to test them.

Don Walker
RV-8 Renesis
44 hours. It's been a busy summer.  I'll start flying again after the air races.