Good job with fixing up the car. Nice to see a bimmer saved from neglect.
Definitely use a torque wrench on your nuts and bolts, especially for the engine. I have a big and small torque wrench. Small one came in handy doing my Vanos seals, valve cover gasket and spark plugs. I almost snapped the Vanos piston bolts when I started to take it off... almost forgot it was reverse threaded!
Did you do your spark plugs? If not they're probably due for a change. Also check your intake tubes, between the throttle and air filter. They tend to get cracks and leak air.
Also, you might want to replace your belt tensioner pulley and idler pulley.
Looks like proper oil changes weren't done or the wrong oil was used. Looked like a lot of sludge in your Vanos. Thought that could be from a failed CCV.
I'm looking at the ISC N1 coilovers, so maybe we can compare once we both have them in.