Charlie run timing at say 10 degrees at 2 psi and start adding boost. READ your plugs! If ok try a 2 degree jump at 2 psi and start sneaking the boost up again. READ your plugs. (Best done on a chassis or engine dyno so you can get an accurate read). Your plugs will tell you what you need to know. (both timing and fuel)
As far as cam goes intake closing point affects cylinder pressure. Early = more, late = less.
As far as overlap goes... nothing can go in the cylinder until pressure in the cylinder/ex port is less than whats present at the intake valve. Small amounts of overlap help purge the chamber while piston is nearly parked at tdc. small amounts of unburned charge help cool exhaust valve but excessive amounts will blow-torch your turbine. Overlap in small proportion allows more undiluted charge as piston descends. No overlap or underlap creates more EGR. Exhaust doesnt reburn it adds heat and takes up space that could be fresh charge.
Mark at Bullet cams might be most helpful choosing what should work best with your combo.
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