So, i used to own a Mini Cooper R53 - Had a Eaton SC.
A common mod for some cheap extra power was to change the pully size. I’ve found conflicting information the more I look. So is it something worth doing?
BW
Yes, but I would heartily recommend you start thinking about aftermarket ECU.
I do not buy into ( and have witness ) the “the lotus ecu will compensate”
It will, to an extent, but not all the way.
For me if I were doing it again I would purchase in the following order
- aftermarket ECU
- everything else
I run a 2.9 pulley, I think @Fonzey does too. I am sure @evo_ufo did as well.
Chargecooler as well should be on your list if going near track.
charge cooler is on the list. Was just thinking of my R53, it compensated fully and was ok.
Ideally is like a charge cooler and bigger injectors + remap.
Honestly the order I stated is key.
The mp62 is already near the outside of its performance envolope as well. Putting more hot air around in the intercooler is not going to yield much at all if anything.
ECU
Chargecooler
Then go nuts 
You can see my progress on a non chargecooled car ( admittedly no IC either ) from here: Exige S2 with added supercharger - #15 by andybond
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