90 740GLE 2.3 DOHC 82k miles (not a typo), Bosch ignition

I bought this car from one of my customers after a minor wreck and put it back together and put approx 10k miles on it before the timing belt slipped and customized most of the valves. Before this, the idle quality had degraded some, but not enough to warrant attention. Always ran great down the road. I run a one man shop, so my cars are the last to get any love. Car sat for about 6 months before it got put back together. After the valve replacement, timing belt, etc. it idles awful, has a horrible hestiation and sometimes will stall at idle in gear or when you take off. Sometimes while sitting idling in gear the idle will vary enough to make it almost stall, then push against the brakes enough to slip the brakes. Along with this, I also have something draining the battery every 4-5 days. I know this sounds crazy, but I've recently noticed that if the "bulb out" light is on it seems to idle almost as good as it did before the head job (though not quite perfect) and the hesitation is gone or much less pronounced. I know it sounds crazy, but it has happened 3 times.

Before I noticed this pattern, here are the things I've tried over the last 5 months: (in no particular order)

Rechecked the timing marks 3x by myself and 2 other mechanics
Compression test - none below 140 on a cold engine
Tested & cleaned injectors
Tested fuel pressure regulator
Checked fuel pressure
Replaced knock sensor
Replaced rpm sensor
Replaced coil, cap, rotor, wires, plugs
Cleaned the oil trap thingy under the intake
Tested idle air valve
Reset the throttle position switch 2-3x
Replaced fuel pump relay
Tested the power & ground to power stage (ignition control module) over by the air cleaner
Did smoke test 2x for vacuum leak
Cleaned MAF
Engine coolant temp on dash seems to be accurate
Been back through the wiring taken apart for the head job and checked for loose connections, pinched wires, etc
Verified spark at each cylinder with a timing light
Pulled plug wires while it was idling rough, each one seemed to make a difference
Put in 3/4 tank of fresh gas

No check engine light or codes

I was getting ready to sell this car before the timing belt mess, and I'm beyond frustrated. ANY ideas would be appreciated. I really need to get this car running well so I can move it down the road.

Thanks

 

If it ran well BEFORE but runs badly now, obviously the repair and/or the parts installed are not up to snuff! Replacing all those parts, if you used cheap Asian ones, any of them may cause problems, wires, plugs, etc. Surprising that you used the "parts shotgun" to cure this... Hard to say after doing so much what is causing it: could be the valves, the belt job, parts...?