Hi,
I used to own a 2003 MINI ONE, I did just about every
mod you could do to a ONE.
The end result was a 140BHP ONE... Now you may think that's not much compared to the 170BHP S's but power to weight that's pretty damn fast!. My ONE only weighed just under 1300KG My 2003 Cooper S is pushing 1600KGS,
And TBH I preferred my ONE, I regret selling it and some lucky so and so is driving IT.
But I will start all over agian with the S

.
Best mods on the ONE.
MTH TUNER ECU RE-MAP
KW V3 Coilovers
Powerflex rear wishbone bushes.
RACE PRO 2 Alloy Wheels (very light)
Other Mods included a nice shiny bottle in the boot

but not really worth it as it just runs out 2 fast
If you have a early ONE make sure you have your drive train uprated as the gearbox is made of cheese

but the engine is bullet proof
Be prep for things to break when your at the 140BHP stage.. your really pushing the limits on what the components where ever designed to do.