I have a 2006 grand prix gxp. when scanning i noticed kr and misfires.

The LTFT's are all +- 5 which is not logged.
Please let me know how to troubleshoot this
could it be normal.
should i look at the MaF sensor.
O2 sensor?
injectors.
or am i making more work for myself.

I can attach tune if someone can help.