But the ECU will simply reduce max. boost pressure if the base ignition timing point is reached and it can't go any further. I had the chip on my E3 changed and they advanced the ignition at the same time. Problem was I had that 104|PLS| octane booster in the tank at the time and when I reverted back to straight 96 (I now use 98) pump octane the ECU went into limp mode , so I was told, and was boosting at the the engine's old stock boost of around 0.7 bar. They must have had the base advanced to the limit still when readjusted because even on a couple of other following occasions on 96 octane the car went into limp mode, but then I'm told our old 96 octane used to go as low as 94 so I must have got a bad batch of petrol on those occaisions or something.