Ford KA - Rev Problem

I have seen a similar post to this below my KA has the exact same symptoms. Basically when the clutch is depressed the engine over revs, it is much
worse going up through the gears and when coming to a stop, the stationary idle is a little high and like the other post I feel sometimes the engine is constantly trying to go faster. I have had it in the garage and they replaced the Idle speed controller, and for about 3 days everything was fine, then it started over revving between gears again. Are there any other things that could cause this type of thing? I was thinking and air-leak somewhere? or can it get gunked up in 3 days somehow? Any help greatly appreciated
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.