02 sensor location / help

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,

Here ya go>>> http://www.boatsetup.com/O2sensor.pdf I know it's not your motor, But it has to be similar..

Thanks once again you are the man http://www.bassboatcentral.com/boardstuff2/beers.gif