Always a good idea to keep the throttle body clean and free of debris , however some manufacturers, notably Ford , specifically say not to do this , as the Tb has a special coating that can get damaged if you take a brush to it . In fact there’s a sticker on the Tb to warn you of this .

Indeed there is. I ignored it. When the EMS light came on in our old Focus for no apparent reason or loss of performance, I googled why. One of the suggestions was a dirty TB. So I cleaned it carefully....and the EMS light stopped coming on. Professional mechanics might disagree, but I think the reason is that the butterfly valve, which must remain ever so slightly open to allow a little air in for idling, lets a in a bit less than it should owing to the build-up of microparticular grot.

Always a good idea to keep the throttle body clean and free of debris , however some manufacturers, notably Ford , specifically say not to do this , as the Tb has a special coating that can get damaged if you take a brush to it . In fact there’s a sticker on the Tb to warn you of this .

That's interesting. The Corsa throttle body looks like very ordinary machined aluminium alloy, and the butterfly the usual coated steel. No warning stickers on it, and we've had the car from new.

The brush I used was a fine, soft artist's brush which couldn't possibly scratch anything, it just helped to lift away the carbon deposits loosened by the carb cleaner. I was also careful not to push on the butterfly, so I didn't disturb its position and confuse the sensor.