Hello Dalibor,
The Mini's racing at Goodwood are 130 HP, FIA Appendix K specification cars running on twin S.U carburetors (more power with twin Webers), and we are only 2 or 3 seconds slower per lap than the 400 HP Ford Mustangs and Falcon's we often race with, incredible from such a small capacity 1950's design engine.
Our engine lifespan is only ten hours before full rebuild though, mainly because of our 8500 RPM limit. Swiftune are constantly developing the engine, however they charge 25000GBP for a new FIA spec engine and gearbox!
The racing is extremely competitive, with ex Formula 1 and Touring car drivers competing regularly in Mini Coopers and we often get race wins if it's wet as the Mini's are superb in the rain as i'm sure you know.
If i'm in Serbia for your Novi Sad meeting i'll come along.
In the meantime, good luck with your Mini and i hope you get it ready in time.
Kind regards,
Neal