Is the yellow engine management lamp on? It sounds like your air mass meter may be playing up. It measures the density of the air going into your engine, is situated just inboard of the air filter, and if there are any splits in the rubber pipe going from the air filter to the engine you get this problem but its usually evident in all gears.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.