I had a similar problem with my 1998 1.6e Sport Megane.
At high revs it would Kangaroo hop because the revs would drop dramatically. At lower revs it would simply stall after the revs dropped below 500 rpm.
It seems to be a problem with the connection to the
sensor and not the sensor itself. The sensor was replaced in June prior to my purchase of the car, however the connection was bad when I got the car and I had to return it to the dealer three days after purchase. The connection was fixed by the dealer.
However, the problems started again about two months after I purchased the car (just before Christmas). At the moment the fix is some plastic clip ties around the sensor to hold it and the connection steady. This seems to be working. I am thinking of fixing a jubilee clip to it as a more permanent solution.
I am wondering if anyone has any thoughts on whether this might be a bad idea.