I know there are a billion threads about upgrades, but I was hoping
someone who did these upgrades could tell me about reliability and refinement. I can't afford the whole kit.

The more I read the more my plans seem to change, but I think this is it.

I have upgraded my Cooper to a 2005 mcsc. Feel the need to go faster and faster.

I would like to do a 15% pulley , belt and cooler plugs, kingsborne wires
I already have the wires but which pulley, belt and plugs should I get?
JCW CAI
JCW EXHAUST
JCW INJECTORS
JCW ECU at dealer

Thanks for the input and I'm sorry in advance if you've answered this too many times. I'm new to the "S"

Do you already have the JCW parts you listed (CAI, exhaust, injectors, ECU tune) but not the other JCW engine parts normally included with the JCW engine kit (supercharger with 12% pulley, ported cylinder head)?

No, but I can get it from Classic for about $1500, intake, exhaust and injectors. I would be installing most if it but then taking it to the dealer for the reflash. Skipping the head and supercharger upgrade.
I am curious to hear if others have done the same and which pulley, plugs and belt to go with.

Donna

Except for the pulley size your supercharger is already the same as the one on a JCW.

I put an Alta 15% pulley on mine 60,000 miles ago it it works like a top.

I'm also using the JCW exhaust & intake. They are very nice & I'm happy with them.

My MINI has stock injectors & tune, but it is fast enough for me & has been rock solid reliable.

Hope that helps you.

That certainly does help. Can you let me know which plugs and belt you run with that setup?

I'm running the stock heat range NGK plug. I changed them out at 50,000 & they looked very good. I'm using a stock belt for a JCW.

If you change injectors & have your ECU reflashed I'm sure you'd want to go a heat range cooler on the plugs.

There is a ton of info to be found here if you don't mind seaching.