Okay, So the check engine light came on last week when I was accelerating hard on the on ramp to the interstate.

Today I diagnosed the codes, this is what I got:
0303 Front Left Heated O2 Sensor
0304 Knock Sensor
0707 Rear Heated O2 Sensor
0210 Fuel INJ sys left bank lean

After reading a little on hear I went and put some fuel injector cleaner and reset the code... The check engine light hasn't come on yet but I haven't driven that much... Should I be concerned about this or wait and see if the light comes back on?

Thanks!