These are the thoughts I had when trying to decide the same thing, so is based on my research and knowledge from other cars, rather than any direct experience constructing all variations of forced induction Minis.
Sounds like turbo might be the way to go for you. If the only supercharger option in the running here is the m45 suck through carby setup then you will probably always have some sort of fuelling issue.
For the supercharger:
- You could look at inlet heating? probably too fiddly to get right and not sure how successful it would be. I know some applications have heated various parts of the inlet. I have also heard that fuel condensation in the charger itself can also be a problem?
- You could look at EFI but that's off the table due to cost which means that
- The option of a different supercharger unit/kit is also likely off the table
- You could look at using a blow-through setup and a plenum chamber (perhaps the Turbo Metro setup?) but I'm not sure that would be straight forward. I'm not sure how familiar with it you are, but you would have to alter the way the carby works, like they did in the Turbo Metro, to compensate for the positive air pressure in the intake manifold instead of the usual negative.
For the turbo, many setups have worked quite well, though if cost is a factor ruling out EFI would that also rule out buying the things needed for a turbo setup? There is a turbo inlet and exhaust manifold set for sale in these forum classifieds.
I decided I wanted the characteristics of the supercharger - broad spread of power and torque.But that's a different charger and setup to what you're looking at.
