I had two flats on cup sports last year. No visible signs of a puncture and turned out to be the tire pressure monitor that they put in doesn't seat itself well. Under load it would slowly leak and i could go flat inside 20 minutes. As I live in Canada we don't have to fit them as the car can use the ABS monitor, so having removed them I have been flat free.
2008 M3 DCT, Jerez Black
Eisenmann Race, custom pipes high flow 300 cell primary 2nd cat delete
AA software, Pulley, air filter, Dinan TB's
Brembo BBK, BBS CH wheels, Dinan camber plates
KW V3 suspension, Dinan 3.62 Diff, Recaro Profi seats, custom harness bar