Gosh, 2.5 years ago - I forgot about this thread...
The light didn't stay off long and has kept coming back pretty much ever since. Usually at about 1600rpm with very light throttle transitioning on the overrun. In the interim, I have replaced MAF sensor, EGR vacuum valve again, EGR cooler changeover valve again, intake throttle that partially closes to increase induction, vacuum accumulator behind wheelarch and checked the system holds vacuum. I have also cleaned where the EGR gas enters the intake with oven cleaner and all inside the pipes, I noticed the flex steel pipe enters the aluminium housing on the intake and there is a sort of swirl nozzle cast into the metal - a restriction that forms the gas into a swirling jet. I cleaned that out too to no avail. The whole EGR system is now spotless and still EML comes on. It is definately working. Loads of exhaust gas came out at idlle when I opened the EGR valve with a hand vacuum pump. The only thing I need to do is test it the same way (visually see the gas) with VCDS output and see if it also works properly. If it does, it must just be that it's effect is not being registered, although I was hoping MAF sensor would satisfy that possibility.
I also filled the system with EGR cleaner that came with a long flexi straw, I filled up the EGR pipes so it flowed into the exhaust and then brushed them with the bottle brushes.
At idle, the EGR was strong enough to blow this hose out with enough force to take the plastic container with it too.
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