The Q2 diff makes the car handle brilliantly!!!, I mean on rails handling, I love it, it's worth getting the car over a standard 147 just for the Q2.
Mine is 150bhp with 225 ftlb so it's a slightly less than the ducati but I usually get about 42-45 mpg but I've done about 400 miles since friday and managed an average of 50.2mpg doing 65-70 most of the way ( I wasn't in a rush and it was mostly motorway)
I had a problem with the egr valve, as everybody has, but it;s a half an hour job to rip it off, beat it up , clean it and re-assemble back on the car
I do intend to get a remap and get the egr disabled.
I had a problem with the yaw sensor which game me abs/vdc faults, but after clearing the fault with a £23 cable off ebay and free software, i've had no other problems.
Other than that I love mine, I know I will be sad when I eventually get rid ( not yet tho!!
I hope this helps