Monro Muffler Brake and Service

AVOID THIS STORE.  Since June 2012 I have had a check engine light on that shows an Evap problem. They have done three smoke tests and two $99 computer checks. They have replaced the catalytic converter twice, a purge valve twice, a vent valve twice and an oxygen sensor 3 times. The longest the check engine light has stayed off is about 600 miles. Either they are using really inferior parts or they don't have a clue what they're doing. Or both. And they keep trying to charge me labor even though their paperwork states "5 years or 50,000 miles warranty" and it has been only 3 years and 34,000 miles.

I was charged $483.36 including tax. My understanding there is a heavier duty bearing which I requested. I had the oil changed this week and the mechanic noted the bearing needed replaced. Please let me know if this work  and the parts are warranted.
I had the mechanic quote me the same job for $265.00. Please explain to me why you have charged me the above rate.