Its always a nice feeling getting the car back with mot passed, the conti or michelin are the best tyres in my opinion for the m3's and good price with fiiting aswell. As far as i know on catalytic converters if you got decat pipes on then it would show a higher reading on emmision tester it could be their machine not calibrated correctly or summat. Try evolve automotive they do some great tuning on these beasts :rolleyes: