5k won't idle till warm

[barry@moonbeast.com]

Hey all-
I'm still trying to get a handle on this idle problem...

The symptoms are that the car will start and may idle for a minute or so, but
then struggles and dies if the throttle isn't blipped to keep it running. 
Afterwards, until it's warmed up, if you let off the accelerator the idle drops
precipitously and doesn't stop until it the RPMs hit zero.

When it warms up, it will idle.  Even when warm though, when you get off the
throttle and the rpms drop past 1k you have to blip the throttle to get it to
settle around 750 rpms or it will just keep dropping until it dies.

I recently resoldered the contacts in the throttle switch, on the side of the
throttle body.  I slid the switch housing rearward so that with the throttle
totally closed it made contact (clicked), and tightened the screw down there:
 
http://tinyurl.com/bd22a

This morning I loosened the screws and moved the switch housing forward a little
so contact wasn't being made at the throttle fully closed position, and the car
is behaving better now.  It will idle, and is waaaay more driveable-- I don't
have to keep blipping the gas pedal to keep it running.  Idle will drop way more
slowly now and it doesn't die when cold.  If I move that switch housing
backwards until the switch clicks while the car's running, the idle immediately
drops and she struggles again.
So how is that switch supposed to be set?  I would think that switch should be
making contact when the foot is off the pedal (idle).  I replaced the ISV with
one from Force5, and it seems to be working- the idle doesn't "hunt" like it
used to.  So do I have the wrong idea with the throttle switch, or am I still
looking for a vacuum leak?  I tried the starter fluid trick with pretty
inconclusive results...

TIA for any info you may have,
=BB=

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