I have a 2008 E61 530i and for the last 6 months it's been juddering under high load at revs between 1500-1800. When it happens, if I don't lift off and reduce the load it will give a temporary engine fault and will run like a dog for 2 minutes before the fault clears itself and runs normally again (until I put it under high load at low revs again). An interesting thing is that it doesn't happen if I use 99 RON fuel (Tesco Momentum). Any other type of fuel 95 or 97 it will still happen. The other interesting thing is that when I had the adaptations reset it was OK for a few days - even with 95 RON fuel, but only for a few days. Some time ago a garage that did some work on it told me that the swirl flaps were ready to fall off and that I'd need a complete new inlet manifold at £450 + fitting. I did some research and found that the petrol models (or this one anyway) doesn't have the swirl flaps like diesels - something different. Where do I go from here?