Check engine light

2001 Impreza 2.5 RS, 60,000 miles

Check engine light code P0420 Catalyst System Efficiency Below Threshold
Any ideas?

1. check for exhaust leaks
2. check for damage at the rear face of either cat

Take it to the dealership. You're still within your 8 yr/80,000 mile Federal Emissions warranty. I rolled mine into the service dept with 79,920 miles on the odo, and they replaced the cat for free.