To be fair here guys, the M has a completely different suspension setup and more than just tires and loss of EPS changes. There's a good chance the M feels more planted which is giving t20 the confidence he's looking for..nothing wrong with that. One thing that I'm not sure has been discussed since this thread is insanely long, is tire pressure. Have you lowered the rear tire pressures? Bringing them down will increase traction back there and might be all you need to solve this issue. The other thing I asked before but didn't see an answer to was your use of DSC. Are you driving around with it fully on? I can't see the back end coming around that far in it's default state.