Reduced engine performance warning

[sdl92]

I have a 2004 S80 T6. The reduced engine performance light started coming on recently. The car slows to around 10 mph and pushing on the accelerator does nothing. Stopping and restarting the car a few minutes later cures the problem for a day or two. I have already replaced the fuel filter, fuel pressure regulator and crank position sensor to cure a hard starting problem. Any idea what might be wrong? Any help would be greatly appreciated. Thanks.