If you say you don't know what you're doing why would you think you should be redesigning the emissions system better than Mitsubishi engineers?

Emissions systems help keep the air clean, but they also keep the air/fuel ratio at optimum 14.7 depending on engine requirements.

Goggle says P0431 is bank 2. http://www.obd-codes.com/p0431


92 Montero LS 3.0L V6 Auto, Stock, Original owner, 185,800K miles