Going through your post here chronologically I hope. Just my 2 cents.
- Radiator flush and new t-stat. Car has 150k. Is this the orig. radiator? T-stat was likely installed correctly - air-bleed valve @ highest point and a quality German t-stat?
- ABS light on - they have been known to be bad out of the box. Not saying this is the case. Had you doubled checked the fuse or maybe fuses. Some OVP's have one; others have 2. Pull them and make sure they're not blown.
- Upper timing chain or upper timing chain cover reseal? Which was it? If the timing chain was replaced, I would hope the timing is correct.
- Were the valve stem seals replaced? Not sure I follow this part? You mention not too oily? If you have oil on the plugs, this isn't helping things in general - oil is finding it's way to the catalytic converter as well if you have oil on the plugs.