http://ecomodder.com/forum/showthrea...p-17904-2.html
I think I found the magic exhaust valve burning A/F.
Yes an EGT might show it.
If you want to use an A/F ratio gauge a problem I see is most of the affordable A/F gauges out there only read A/F out to about 15.5:1. Slightly leaner than 15.5:1 is where I believe the valve burning happens.