engine trouble code questions

All right, Just got back from Auto Zone and I have 4 trouble codes...
1. PO 420
2. PO 110
3. PO 101
4. PO 100
These are for my 02 V6 prerunner and it still runs good but uses a bit more gas then normal. My exhaust did have to get fabricated due to a miss-measured cross over pipe thanks to JBA, also I have my K&N gen 2 intake system and a raven performance exhaust. Should these codes really be of concern or should I just not worry. Auto Zone stated I should get a power programmer to help with the adjustments due to my aftermarket add-ons, does anyone know where I could find on for my taco.....a little help please

Clean your MAF meter, both the electical connection and the part of the meter internal to the intake. Make sure the connection is tight.

Check your HO2 sensor.

Replace either of these if bad (HO2) or can't clean it (MAF).

Both these are important