Trouble Codes...

[blageo23]

My check engine light has been on. I finally went to checkers and got the codes. This is what I have.
P300-Random Misfire
P170-Fuel Trim Malfunction-????
P136-O2...
P141-O2 Heater...
Clearly the last 2 are because I dont have the rear O2 sensor pluged in and the first one is because I did the 6Bolt swap. But what is the 2nd one? Fuel. Could that be why my car shakes. Now that I think about it it could be lack of fuel. Everything in the fuel area is stock and I just replaced the Filter like in september. The only thing not stock on the fuel is that I caped off the line that goes to the emisions(gas tank vent). I have it still pluged into the soleniod(vac lines).