Hi there, this is my first post here after lurking around for a while. So a couple of months ago I bought my first car, a 2004 Cooper S JCW. So I wanted to get a CAI and I found one used near me and I bought it. But, the guy also gave my the bottom tray area for the filter with his ECU attached.For now I just installed the intake into my car and left out his filter and ECU. I know his was an 05 JCW so would there be a difference if I switch the ECU's Ie. a performance difference or would my car explode. Is there any point in me keeping it or should I just sell it.

 

There were two JCW Engine Tuning Kits ... that latter version included the JCW airbox and larger (380cc) fuel injectors with an ECU remap.

Are you saying you have the early kit and bought the airbox from the latter?

I don't think you can swap ECUs. If you don't have the larger fuel injectors you wouldn't want the ECU remap for them.

1st Gen MCS JCW Tuning Kits - The MINI Wiki

 

I am pretty sure that all the senors on a MINI are "addressed" in the ECU so if you tried to change to another ECU, that ECU would need to be reprogrammed to recognize your sensors.

 

Yeah, I would not go there, as cost to do the DME to know your Vin is costly and most Mini dealers can not do it. You need a DME/ECU rebuilder with the right software and equipment to match the new DME. ( maybe a few dealers have this capability, as I really don't know of any)
Used DME/ECU are not really worth anything, as a new one will set you back around $400, if you know where to get one. I bought a new one out of the UK, for that price. It is blank, so you can easily put in the vin and software for you VIN. Either way, it is a bit tricky and requires some specialized equipment, including a 90 AMP battery charger and a rock solid internet system. One online glitch can render it useless, as many have found out!