Is it a late IVC, late/early EVO, or overlap?

 

I think its overlap. When the valves are opened longer at the same time, there's less time for a fresh intake charge to come in. It's mixing exhaust gases with the fresh intake charge coming in, exhaust gases are an inert gas(doesn't burn). That's why when your at idle with a stuck open EGR valve, it causes a rough idle due to the fact that exhaust gases are getting mixed with the intake charge. Same affect with a camshaft.