2005 Kia Rio Car stutters?

My car did this once before and straightened itself out. This time it won't, so I need some help.

When starting it starts correctly and promptly, no issues aside from the engine light being on. Was told this was a MAFsensor/air filter code.

I put the car in reverse, apply gas and it will move than act as though there is no gas getting to it. Sort of like it will die but it never does. When letting go of the gas it idles normally. I cannot get the car past second gear due to the lack of power/gas/air or whatever.

I was told the O2 sensor on bank 1 was reading too lean, but I would think that means the sensor is fine since it can read what is wrong.

Question is, how do I fix the problem, and what is the problem?