I have a vague memory that Mike's Tank was remapped from 90 to (120?). IIRC he also found that his clutch needed to be replaced more frequently. Because the 90 uses a dual-mass-flywheel rather than the simpler single-mass-flywheel in the 75, the clutch system is more vulnerable.
There are a couple of 90s remapped too - as it has a completely different turbo to the 75 and is capable of higher output - 120BHP is possible. The word of caution with remapping the 90 is not to over-do it on the torque as a remapped 90 is capable of generating more torque than the clutch/flywheel assembly can reliably cope with if it is dialled up to the max!