k my service engine light came on again now the codes 420 and 430 are popping up...which is catalyst on left bank and right bank are inefficient....what does that mean....and most likely what is it that's going to have to be done in order to fix the problem???? I'm not sure if my warranty covers that or not....because I don't know what it's talking about...somebody help please....oh and its a 2001 Z28 LS1 (V8)