oddball RFI problem

I recently installed an EI FP5L fuel flow instrument in my Tri-Pacer. I
would notice that at irregular intervals, it would reset it self. I'd catch
the green Remaining LED flashing as it does after a power on self test. I
could never get it to fail in flight. I pulled and prodded all the wiring,
replaced the circuit breaker, tapped on the instrument, etc etc. Talking to
EI, the mentioned the possibility of RFI getting into the thing. I keyed the
radio on all the frequencies that I normally use and again it didn't fail.

Next I returned the instrument---you guessed it no defect found!

Well when I got it back I hooked a battery charger to the plane and turned
the master switch on and let it cook for a while. After a time of trying all
different combinations of stuff turned on and off to try to make the fuel
monitor reset, I finally found if the radio is keyed WITH the strobe on,
bingo !! the fuel flow resets.!!!! The strobe is mounted on the vertical
stabilizer. All grounds are run to a good common ground with the exception
of the strobe which uses the airframe as a return.

I haven't checked the SWR on the radio yet, but for the life of me I can't
figure out why turning the strobe on makes the damn thing reset when keying
the radio.

Although it did it in the hangar, apparently this isn't 100% true in flight
since the strobe is always on, and the thing resets intermittently.

Anyone have an idea??

Thanks

Paul
N1431A