I stored mine coupe for the posterity, went with a Lucas Blck Tag rack. Is actually quicker than any other BMW rack at 2.5 turns lock to lock.
The z4M coupe rack is not any “quicker” than the CSL, or Yellow tag, etc. it has built in limiters and that makes it 2.8 turns lock to lock.I measured my coupes rack and it displaces the rod 50mm per turn but has only 140mm of full travel due to those limiters. E46 chassis racks have 150mm of displacement. So that alone gives the illusion of being quicker, but is really the same as any other “quick” rack from BMW
The black tag rack is about 60mm of rack travel per turn.
The quicker steering ratio on the Z4M chassis’ come from the kingpins, not the rack.