mine r56 has done 690 miles now going back on rolling road soon for another session i've already given it a few good kickings and just sounds perfect and the best bit in 500 miles it has used 2mm of oil on dipstick uses next to zero even on the run in time span,, the trick is the new piston rings i always push them in bores after the hone and feel gauge the gap on the piston rings and file them accordingly as i ordered slightly over size and made them fit with 0.10mm gaps so by time run in should be 0.15mm then when add power the heat range should closed it again as such,, on nos fed cars they gap them 0.30mm -0.40mm as rings expand with heat and if to tight will not allow the rings to move in the slots,,, ie piston rings must be allowed to rotate after fitting, also the gap need to be 180 degrees from each other on two compression rings i set them 11 oclock to 5 oclock and then set the oil rings the same way on a 40 degree off set,, i also use grease and oil for bearings and valve stem seals when installing them gives it all chance to get oil before running out of lubrication,, nothing worst than building something to start it to get a sticky valve or crank bearing spin,, mine sounds like a new engine now no rattles even when i cant the idle is that stable that after cant feel it running its proper good,,,