2001 2.4 Vvti Previa Auto

[stemac33]

Hi all in need of assistance. Right got a 2001 2.4vvti previa auto about 6 months ago ran perfect until now, the car has been stood for about 6 weeks started every week for about half hour, came to start it today and started first turn of key as usual but after about 10 mins the revs where still high so revved the engine and they dropped down abit revved it again and they dropped to normal, revved it again and when it dropped back down it cut out. Has done this every time it has been revved now, so took it for a drive and when you brake at a junction and the revs have to drop back down it cuts out, starts back up first time without a splutterand idles ok until you rev the engine. got me stumped, Any Help would be most appreciated

Cheers

steve