Kinda late on this one, but....
Did you polish the intake ports? Intake ports shouldn't be polished, (that's what they say nowadays) the injected fuel will, in many cases, "wet out": liquid gasoline doesn't burn. At higher rpm's, it's not such a problem, there's enough airflow to rip apart drops of gasoline, but at lower rpm's a matte or slightly rough finish to the ports will give liquid gasoline enough traction to be picked apart by the lower airspeeds. It may cost a whole horsepower or so in an allout tuning effort, but it's becoming common practice simply due to the driveability concerns. But that's just a possibility! Check the easy stuff first, vacuum leaks and so forth.

Porting the head didn't change the fuel air ratio. Neither did the cam. The mass meter meters the air and adds the fuel that it needs. The O2 sensor checks all that. Something got misassembled or damaged. You don't need bigger injectors. The ones you have will flow for quite a bit more power, and changing them would need a computer change anyways.

Have you checked the vacuum with a vacuum gauge, do you know what the vacuum was befor the work you did. With the higher lift cam and smoothing out of the intake passages you may have caused a higher flow of air to enter the system. I'm not sure the injectors from a turbo would help as much as an ecu from one.
The 02 sensor might be the culprit as listed in the last post and indeed would be a good starting point, also check the vacuum going to the fuel pressure regulator, if your not getting vacuum there it may cause a lean condition as well.
Th 02 sensor should react to a lean condition and give the info to the ecu to give more fuel , how long since it was changed last.
Hope that helps
Poolman

Faulty oxygen sensor? Or the connection on it is bad/dirty? The ECU uses the sensor to keep the car in tune.