John, I know i'll get flamed for this, but definitely go PCM. I resisted it in spite of problems, but on a landing approach, a glitch can be a crash.

A loss of control for a second should not be masked with a PCM receiver, but a few milliseconds control loss is no big deal.

On another note, nothing interferes more than ignition EMI. I found the spark plug clip inside the boot was a teeny bit lose. The rattling around, ever so slight, of that connection gave me an intermittant glitch just like you describe. Squeeze that baby down till it is really hard to get on and off.

I talked to the Radio South people about my problem before I went to PCM. I was advised to go PCM. They called FM russian roulette.

When I told them I knew scads of people besides me flying FM without problems. They said they knew plenty of people who played russian roulette successfully for a long period of time, before they blew their heads off.

I have now acquired enough PCM receivers for all my gassers, and each time a buy a reciever, gas or glow use, I go ahead iwth PCM. Yes, it costs twice as much, but receivers last forever.

As for masking problems, here's what I do. When I range check, I set the idle down switch for low idle. Then I set the throttle stick up a couple of clicks so that the difference in RPM and sound are significant. If I glitch on range check the engine throttles back, because I have the fail safe set for low idle. This is working for me, something to think about for you.

Hope this helps,