[niles]

You didnt mention cam specs. But with much duration and "lower" compression, the flame velocity is lower, possibly allowing a lot of burning in the headers after the exh. values open.
Turn inital timing up to 18-20 deg; what happens; engine speeds up about a 1000 rpm; why? more time is created for more gas to be burned in the combustion chamber, creating more energy/rpm with less going into the exhaust creating less EGT
cheers gn