Kia Sportage 2000 Engine Problem

My kia sportage 2000 works fine when the motor is cold but when it warm op then it starts running at 1250 rpm  and when i'm stopping at red lights the motor stays at 2000 rpm until 3 sec after complete stop  then it drops to 1250 rpm again. if im stop on a hill with the car in neutral and release the brakes the rpm goes up to 2000 rpm again,  until 3 sec after full stop it drops to 1250 rpm. When I´m driving doesn't matter which speed and put the car in neutral the car stays at 2000 rpm until 3 sec after complete stop. ?? why is the car then increasing the rpm op to 2000 when it moves in neutral it's 5 geer ?? The is no engine light and no error in the computer. I have changed  sparkplugs  gas filter  massair flow sensor  idle speed control  injection position sensor I have throttle cable my car and it is with a slack my car is manual 5 gear.