Patience NEWBIE
The 98 Legacy 2.2 L has 150,000 Km's (90,000 mi) and has never had a fault. This MIL P0420 just came last week.
The local Subaru dealer made no more detailed analysis than I did with my OBDII tester. They wanted to first replace the rear O2 sensor, then the cat. (300+1000=$1300 CND). Whoa. BUT I got an OEM Bosch O2 sensor, then had a good known pipe bender replace the Cat. I have spent $350, BUT still have the P0420. Before I throw more at it, does anyone have a knowledge of this problem or at least a better troubleshooting scheme?
I would appreciate any help.