A friend of mine has a mk1 golf gti fitted with an audi tt 1.8 5v turbo lump. The car and engine ran fine until he changed the turbo for a hybrid and now when its gets up to around 4k revs it splutters and misses when your floor it, but if your light on the throttle it will rev to 6kish before it does it and its only a tiny amount. We changed the plugs like for like, also replaced the pencil coils for new ones and it still does it. But un knowing to me till now they fitted a new forge actuator when they fitted the turbo and I can literally pull the waste gate wide open with one finger!! So my thinking is as the tps is telling the ecu that the throttle is at wot and then dumps the fuel in accordingly, would the fact that the boost is dropping off so quickly its flooding the cylinders and causing the misfire ?

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