Took the blazer to have the codes run on her today. Two came up and I have no clue what they are or what to replace. Can someone help?

Codes: P0410 - SECONDARY AIR INJECTION MALFUNCTION
P1416 - MANUFACTURER CONTROLLLED AUX EMISSIONS

She's getting really bad gas mileage, want to get it fixed asap.

Sounds like you air pump is not working which would give you the bad emmision reading.