Get an old spark plug. Next time it won't start pull a plug wire (I helps to have the proper tool.) attach it to the old plug, ground the plug and have someone crank it while you check for spark.

It sounds like you're just throwing parts at it. This simple test should eliminate the ignition system or indict it as the culprit. Electrical intermittents can be tough to find. Check all primary and ignition system connections including the TDC sensor wire. That's what the EZL uses to time the spark - no TDC pulse, no spark.

Duke