I have a 04 300 Vmax, last October I had a shop replace the fuel pumps due to loss of RPMs it would go from 5k down to 4200, (that fixed the problem) now 5 months later I am haveing the same problem, I ordered new pumps today but then I was told to look at the O2 sensor, can anyone help me out with the location and any opinions on this would be great,