I am having problems with my new secondhand meriva - its a 2006 version and has the anoying habit of increasing revs after releasing the throttle after the engine has been under load in a low gear and you try to change up. This happens for instance when climbing a hill and the revs get to 2500+ for a while and then you change up - it increases the revs before settling back. The garage (Vauxhall main dealer) has put on the up to date engine management software and checked it but cant find a fault and dont seem to know what to do next - any ideas what it is?