Definitely start with the ecu, the power gains are definitely noticeable. I used a nm power module and currently using burger jb4, both really easy to install. I prefer the jb4 because you can also add a bluetooth device to get read outs on your phone( oil temp, air intake temps, boost) and you can adjust what map you want to use depending what other upgrades you do. After that I would do a upgraded exhaust and intercooler that way you can run on map 2 and get the most out of your tune. Good luck!

 

Not trying to be an ass, but i'd recommend starting with the grippiest tyres possible first. We (JCW owners) struggle with the already existing power under full throttle outside of ideal circumstances like warm, dry, nice and flat asphalt until like... 60 km/h?. More power will give you noticeable gain only after like 70-80 km\h (roughly speaking, never measured properly). Plus, wheel hop on wet is a b%tch.

Other than that: intercooler, ECU tune, exhaust (decat is optional) usually reach sub-300 HP.

 

Agree with all comments, just had my 2018 stage 1 ECU map done a couple of days ago and the gains on an already nice grunt are noticeable, thinking I am going to look at the exhaust and intercooler next. According to the blurb my stage 1 has an additional 60 bhp on the 231, not sure if that's true without taking it to a rolling road (may do as well), but it feels good, and the extra torque from standing, sweet. Enjoy whatever you decide to do 👍

 

The first thing to do is to train yourself to use the power you have. Couldn't agree with @LazyLancer more. The JCW is tyre limited. I had to modify my driving style and be more progressive with the throttle when I first got my JCW - otherwise its torque steer and wheels spinning.

The second thing I would do would be to ditch the runflats, get some PilotSport 4's or similar and go to either a 215 or 225 section tyre. Then think about adding power .