The MMT is why I suggested trying to find a different fuel supplier. Unocal-76 100 octane does not have any metallic additives!
Read the specs here:
http://www.cosbyoil.com/racegas.htm
"Sunoco GT 100 contains no metallic compounds to harm catalytic converters or oxygen sensors"
I have several choices in my area, including Torco, Unocal, and Citgo race fuels. Unocal is my best choice because it's MMT free and isn't blended to order by the tanker driver. Torco has had some supplier troubles when they mix the octane wrong during delivery.