JVR6

I have a Golf VR6 here that actually has a Sharan VR6 engine in it. There is something very wrong with it, it starts and idles ( a little lumpy) then as soon as you rev it, it either dies, or bogs down to nearly no revs and sometime backfires in the intake. it also smells of petrol real bad when this happens. i cannot get it to rev over about 1.5K. i took the plugs off and they didnt look too bad, what else is there that can help me narrow down the problem? any help much appreciated.