I actually have a four part question.

1. What do the codes P0304 Misfire Cylinder 4, P0420 Cat Efficiency Low Bank 1, and P0171 System Tolfan Bank 1 mean?

2. What can cause each of them?

3. What is the best way to fix them?

4. Could the problem have been caused by work done about a month ago by Mr. Tire? They did a tune up.