First rough idle youth now it won't accelerate over 2000 RPMs?

I have a 2003 Nissan Sentra today it started idling roughly. When I give a gas in park or neutral or even when I'm driving it seems to accelerate normally but when I take my foot off the accelerator in the car returns to idle speed it chugs as though it's running on only three cylinders it eventually smooths out but just tap the accelerator and it returns to a rough idle for a few more minutes and then again smooths out. I just took it to our neighborhood mechanic they know it's not the plugs or wires but when he reached his hand behind the throttlebody it smoothed out. I don't know what he was touching what it was near where the air filter connects to the aluminum intake manifold. He suggested we run a can of throttlebody cleaner through it we did but he says it still didn't fix it a computer reading read several different error codes but he believes what's causing this behavior is the code which indicates the mass airflow sensor is bad. While the car acellerated normally on the way to this mechanic after the mechanic it will not accelerate over 2000 RPMs while the car is in drive but if you put it in neutral park it will raft of five or 6000 RPMs he said he used his computer to reset the codes to clear the codes but I know those computers can also be used to set the RPMs do you think he limited my RPMs he says that when I replace the mass airflow sensor the car will return to normal . I think he reprogrammed my chip I know there's a lot here but I would appreciate as much input as possible. Thank you