Have you tried the Air Mass Meter test. Keep the key off (don't ever try this with the key on). With the key off you unplug the air mass meter and if it idles better then its the problem. When finding a spare your going to need one with the last 3 numbers 016, found in both the 240's and 740's. They range from $10 to $50 used. New they run a weeks pay.

I also like the Ken's suggestion about the crank sensor. Its behind the engine block on top of the bell housing. I can reach it best from the passenger's side. You can barely get sight of it. I just go blind changing it out. Make sure to wipe oil and junk off around it before unscrewing the one 10 mm bolt. The wire can also go bad on it.