[Shotimes] My '93 SHO is stalling, mechanic says idle motor> (?) is issue

[Aaron Lowe]

Wow, I'm overwhelmed by all the responses/advice.  Thanks so much, 
especially to George F. for the detailed replies!  Now that I've filtered 
through all this and tried to absorb as much of it as possible, I have a 
couple of follow-up questions ....

(1) If indeed my mechanic did install an incorrect thermostat, how serious 
is this?  Should I insist that the cooling system be drained and a new, 
correct thermostat be installed?

(2) I located the invoice that I was given the last time I had the car in, 
and here is what he wrote:

Oil pressure light flashes on a couple of times at idle.  Idle problem is 
IAC motor.  P - $63.44  L - $62.00.

I knew he said "motor" in relation to my idle problem -- is this the same 
as the "idle air bypass valve" that George was talking about?  My stalling 
problem is becoming more and more prevalent, so I do want to get it 
addressed as soon as possible, but I want to be sure that I'm not throwing 
money at the wrong problem.

Thanks again, everyone, for the suggestions.  It makes me feel really good 
that I'm not alone, and that these problems don't seem terribly uncommon.