What do i do about my Alfa 156 2003 management light comes on lose power when you rev high what could it be?

Several things, I had the same problem though and this is how I sorted it. Basically under hard acceleration the Motor Control System Failure light flashed and the car jerked as if it was been starved of fuel. I bought a diagnostic kit and but there were no error codes registered so I couldn't determine what the problem was. I ran injection cleaner through it and that didn't work so I checked the plugs. Cylinder number 4's plug was rusty on the outside. Eventually, the MCSF message stayed illuminated and the diagnostic showed it as being a temporary miss fire on cylinder 4. Bought a new coil pack, fitted it and haven't had a problem since. I'd aim for that route if I were you (get a diagnostic kit for about £40, a new coil pack costs about the same) Failing that, get a second hand coil pack from a breakers yard and swap it with each coil pack to see if it solves the problem. Hope this helps. I'm assuming yours is a 2.0 JTS btw. That's what mine is.