OK guys, here's one to think about.  Problem:  Major mis-fire at 6600 - 7000 rpm.  Engine runs great up until it begins mis-firing.  This is a 20B running an EC-2 that's been updated with the latest s/w (as of 9/1/07).  This includes the snubber fix and a modification for the Renesis CAS.  Before the snubber upgrade, the engine ran good in the upper rpm range, but not in the lower rpm range.  After the snubber upgrade & Renesis CAS modification, it ran great in the lower rpm range, but had a serious mis-fire beginning around 3800 rpm.  An attempt was made to correct the mis-firing problem by installing a resistor/zener diode circuit in the CAS lead (this strategy worked for another Renesis flyer).  This approach was partially successful, but only up to the mid 6K range.  Multiple phone calls to Tracy resulted in no fix.  I think he's hiding in Colorado so he won't have to take my calls. (I'm kidding, of course.)  Finally, today (after months of struggling) I discovered what was causing the problem.  It now runs great up to 7300 rpm, verified by a full-power run down the runway.  Anyone want to guess as to what the problem turned out to be?  Mark S.