Hello first time cobalt owner its an 06 cobalt ss sc, has close to 142k, and only mod is injen intake. So recently it has threw the P0420 which I seen it would most likely be a bad cat? Also threw a P0103 for MAF, P0171 fuel trim system?, and a P0300. Are these related to a P0420 or all seperate issues of there own? Just need some advice on where to start as I am new to chevys and thank you in advance!