Recently I filled up my tank with normal unleaded fuel as I was in the middle of no where on a long drive and could not find a Shell garage. My BCS was F****d at the time so was not driving it around hard.
After getting the BCS fixed, the car was boosting again but the power felt so flat and I though that there was something else wrong with the car as it felt so much slower than before.
The tank emptied recently so re-filled with V-Power and when I floored the loud pedal, it was back to its powerfull self!! Couldn't believe what a difference petrol could make. I know the car is mapped for super unleaded but didn't expect it to drive so badly on the normal stuff.
So don't fill up with normal unleaded if your car is mapped.