It's been interesting to compare the GT3 Z4 (red) and the GT2 variant of the M3 (blue) at Monza this week. Graphs from top-down: BRAKE / GEAR / SPEED / THROTTLE / TIME DIFFERENTIAL Edited: got the red and the blue around the wrong way!! Sorry! The above colour coding is now correct in initial description. But this now actually confirms what I thought before carrying out this test. The Z4 is slightly less fast than the M3 on the straights - but because of better downforce the Z4 is better in the corners. This Z4 trait -- in relation to other cars (not M3 in the following series) tallies with what has been observed in Blancpain and also FIA GT in 2013.