Wild stab in the dark here......Camshaft is possibly off one tooth on the chain. Get brave at this point and pull the timing cover to look at it. Other ways to check, but at this point, simpilest way to be sure. Weird possibilities from mis-machined timing gears or somebody at the cam grinder had a few too many margaritas for lunch messed up. I don't feel that's the problem though. If the cam is off (probably too advanced), this will cause the symptoms you describe.