Can be a few things mate. I had this on my old mb6 when I bought her back from a guy who's only had her 3 months. He'd replaced the front tyres with very worn ones, one of which was worn right down on the outside. The tracking was also out. With this combo, I ould change lane on the motorway just using the accelerator! mega scary. Same as yours, accelerate, it pulled to the right, back off the throttle and it would shoot to the left. Two new tyres, tracking done and she was as good as new. So that's your first port of call.
If it isn't that, it will more than likely be th front wishbones that are gone. The place that does the tracking will be able to advise you of this though, as they willbe unable to track it if the wishbones/bushes are shot.
Hope this helps.