My 97 QX4 failed emission inspection because of the following codes P0440 and P0446. Any ideas on what they are related to?

http://www.iequus.com/obd_def.asp

I had P0420 and P0430 on my 2001 QX4. First, one of local mom-and-pop car shop wanted to replace all my catalytic convertors, but my dealer upgraded the ECU software.

Its your vent control valve on your EVAP canister, right behind your driver's side rear wheel. Most likely you'll need to replace both the valve and the canister, should be under $100 for parts last time I checked.