Chevrolet Matiz Throttle Body Problems

The revs are very slow indeed to come off when changing gear, the car has only done 18,000 miles and has been checked at Chevrolet dealership who found no fault with diagnostic tests, and commented it was a design fault with this model. I ...

Same as below, checked everything for air leaks etc did the below get fixed and if so how?

The engine is holding the revs up (1500-2000) before settling to tick over quietly after about 15seconds. The revs increase a lot between gear changes going up but not usually when coming down. Using a lot of fuel. Seems like an air leak bu...