So, I didn’t diagnose anything tbh, I just took the manifold off, took all the flaps out, took the motor off and threw it all in the bin. Absolute pants idea if you ask me. All they’re supposed to do is make the idle smoother, but my car actually idles smoother now than it ever has before. Plus, I’ve seen many cars get scrapped because the flaps fall off, break up, and get sucked into the engine. Then hey presto, no compression. While I was there I cleaned out the EGR (which does nothing) and throttle body, and replaced all gaskets. The inlet manifold flaps have absolutely no part in the DPF regeneration. Drives much smoother, quicker and more responsive. If I were you (which I was) I’d get them out before they fail. Let me know if I can be of any help 🤘🏽