Hey guys, I have a 2004 holden vectra the engine light is coming on when i come down hills. It stays on once ive come on to flat land and I've got no acceleration when it comes on, When I pull over and put it into park it just starts revving but doesnt do anything when i press the accelerator when I turn car off and switch back on again it just keeps stalling. Once I leave it for about 10 minutes it seems to come right again.

Does anyone or any machanics know what this might be. I've been told it could be moisture in one of the sensors and the computer in the car is picking it up and switching engine light on the engine was cleaned by a holden dealer a few weeks ago.
I will be taking it in to a holden dealer to get them to plug there computer into it and see if its coming up with anything but if i can figure it out without taking it in would be alot easier.

Any help would be appreciated