After driving with the check engine light on for quite awhile I went to a local shop and paid to have them tightened up once again. The mechanic there had the cure for the cats coming loose. He claimed a lock washer and a second nut would not allow the cats to back off. First trip on the highway a few days later (not even driving hard) the cel light is back on with the same exhaust codes. What is different between the mounting ends of the Solo cats and the stock cats which never come loose? This is ridiculous!!!!