My 2001 prizm has slow throtle response on take-off and passing??

What is your question?

My 2001 prizm has a problem with the throtle response and it cuts off sometimes when I first crank it up. I have had a diagnostic run on it and it came back with left bank too lean or O2sensor so I changed that and plugs but the light is back on. I know it has to be somthing simple because other then that the car runs out great but fuel milage is still lacking a little on the hwy as well. Any suggestions would be great. Thanks, Jon.