Lean after CAM swap

I just swapped out my cam and valve-train components in my heads, and ported and polished my exhaust and intake ports and base tuned. Drove fine for a couple days then it didn't start. Engine light started flashing when I did finally get it started so I hurried up and in the laptop and plugged it in. P0300 Multiple/Random misfire. No leaks, had the head off didn't see anything. Shut the injectors off one by one and they all work. And no mix in fluids. Is it possible that when I ported the head I thinned out a port and it crack that way? Any other ideas? I gotta get this thing running again. Please help. Thanks in advance. -Eric