Engine vibration is still present after many attempts to alleviate....

Symptoms: Have some engine vibration at idle and in neutral (but tolerable), much worse when I put it into gear (I shift out of drive while waiting at a light just to avoid the vibration!). Once RPMs are above 1000 or 1200 rpm things smooth out and vibration seems to go away. I see no smoke at idle or under load when driving.

I have done motor mounts, tranny mount, adjusted valves, and rebuilt the injectors with new nozzles and balanced them. By now, I expected a smooth idle!

From reading on the forum, sounds like other things to check are:
-compression (I fear this one because I know the fix is not easy!)
-injection timing
-timing chain stretch
-air getting sucked into fuel system somehow

Any one willing to wager on which of the above it is, or have any other ideas?

(I have a similar post under a topic related to removing motor mount bolts. Thought it fit better under a new thread with a new title since the topic is somewhat different now, sorry for the redundancy.)