My petrol cooper has developed a slight power loss. It struggles a bit going up hill and occasionally there is a slight blip in the acceleration as I go through the gears.
The emissions warning light came on but was switched off by diagnotics guy at the garage and has not come back on since.
Is it a catalytic converter problem?

Hi ya

It could be the pre cat O2 sensor, but it could be lots of other things, get it plugged in to a diagnostic machine.
See if there are any codes stored not all codes bring on the EML light

Hope this helps