How long have you been running this engine? I am gonna convert my asp twin to cd ignition with one of C&H's units, The plugs are $15 a pop, but should last in excess of 75 hours on glow fuel, the batteries for the ignition can be smaller and will last longer than with on board glow. With synchro spark the engine will idle better and according to tkg(dude from c&h) it will reliable burn richer and leaner mixes. It may be expensive but I am confident it is worthwhile

My twin will drop the left hand cylinder on a low idle, but comes back to life when I throttle up, it is really wierd, I used my IR thermometer (Bill's advice) to check them, when both cylinders are firing they are within 30oF of each other (but only just), through-out the throttle range.