Sprint Booster relay is an easy upgrade for the throttle responsiveness. You can also upgrade the air intake with a cold air kit. Then you can do some turbo heat shielding and wrap your headers, followed by and upgraded exhaust. Don't forget a short shift kit and lightweight flywheel to op it off.
1st there is no pulley in a Roadster (not super charged, but turbo) Tune ($500- $1000)(N18 of course you will void the warranty on the ECU by getting it tuned, it requires bench tuning) CAI (Cold air intake) ($200 - $400) not much of a speed boost but lots of fun noise up front Exhaust Good performance and noise ($800 - $1200) not installed Turbo cooling (AeroGel) ($250 - $500) keep the turbo cooler for more power ...Many many more Myself I would focus on the Nut behind the wheel and the suspension. MINI is corner fast dont compete strait line.
Search MINI Roadster Questions
MINI Roadster Experts