Air Flow/Exhaust censor causing this?

It all started when I had a power steering pump installed. I got the car back and drove it home and punched the gas and it felt like the fuel line was being squeezed and not letting enough gas through.

It happened the next day as well so I replaced the plugs, rotor, distributer cap, fuel filter, air filter and took off the connectors to my fuel injectors and the wire going to the box thing on the big air hose (is this the air flow meter?) when I touched the air flow meter it it affected the idle in a positive way so I cleaned the connection and put light bulb grease on it and taped up the boot.
It wouldn't run worth a damn-like no power.

I took it to the mechanic and he said he replaced the fuel injector wires that I had messed with-they are quite old-and it was fixed.

It drove home fine but this morning it did it again. It seems to have a problem running smoothly when it's cold-could this be a wiring thing? When it warmed up it seemed fine.

I checked the error codes and one was the exhaust sensor and I forget what the other was at the moment. Please help! I'm going broke and my Maxima is driving me insane!