I like AFN engines. I even have one in my 1960s mercedes. There is however one problem with them, EVERY TIME once every few weeks the vnt gets stuck. I have no idea why. I have tested the injectors, fuel system, turbos, everything. I had a lot of afn engines in various projects, some old some newer, and they all do that. In my benz and my quattro i actually have an adapter i made that fits on the old egr hole and has a removable plug (actually a lambda blockoff plug) you can quickly take out for injecting oven cleaner!

The only thing i can think of is the map. Im using a ~150hp map from some random tuned ecu that i found. I dont really know where it came from but i read the memories of the two chips and kept copying it. It drives really well so i keep using it. But maybe its not a good map?

And body know what causes stuck vnt syndrome?

1) mechanics. The first edition of VNTs were prone to plugging with carbon, I experimentally tried adding Eolys 176 (I hate repeating myself) to the fuel and ...unluckily for me... the VNT got unstuck and started regulating properly low boost.

2) the VNT has a VERY sophisticated control loop if you care to look at it in the Bosch manual. it could be driven to any limit levels as governed by the control loop if you look at it.