abrookey

First off, I am new here. I recently bought my first M5, a 2006, SMG. Had to immediately replace the vanos oil line in it and the fan...Oh joy. A couple of questions.
1st. Every three months or so, when starting the car the "elevated emmissions" light comes on, stays on for a few days, then goes away. Had it diagnosed, 74 random misfires, but no one knows why, everything checks out perfect.. WHY ???
2nd. sometimes when it gets to about 2,500 rpm or so, I hear, what sounds to me, like valve clatter. Reminds me of detonation, in an older car when the timing is advanced a bit to far. If someone is in the car with me [added weight I presume] it seems to do it more often. Vanos? Is the vanos adjustable? I need some serious advice here, not much hair left to pull out, looking for a stick of dynamite.
Thanks