Stalling when hot.

A problem just cropped up on my 95 GT. I don't think it has anything to do with the changes I just made to the car but here's what I just did.
New clutch
OR X-pipe
Removed smog (plugged vacuum lines)

Just recently the vehicle is stalling and won't keep idling if it get's hot. We've been having some warm weather lately and I've been driving the car now more than ever trying to break in the clutch.
At least three times this week once the engine was good and hot the car will stall when I come to a stop, will restart, but will immediate hunt for an idle and eventually stall.
The car does have some time on it (125k) but runs great when cool. It has a fresh tune up (plugs, cap, rotor, wires, fuel filter), and didn't blow any codes last time I checked. The cooling fan does work fine and the cooling system is in order.
So far all I've checked was the fuel pressure. I did it today when the wife came home and it was doing this same thing in the driveway. The fuel pressure was a steady 30psi while running, but once the engine started to stumble it would rise slightly and then become steady again.
I'm not exactly sure where to start, but heat related issues usually point to electrical items. Does anyone have a good starting point for me???
I also want to check the timing. I'm getting a lot of detonation (spark knock) when I really lay into it, and I noticed that someone before had marked a couple spots on the balancer. I want to know where it's at as well.

Update

This probably has nothing to do with the stalling problem.

I just came in from checking the timing. The guy before me must have played with it. It was set down around 5 deg., and correct me if I'm wrong but 10 deg is where it should be. I dialed it in at 13 deg and called it good.
However, and this might be a different post all together, when I took it to my local "test street" (I hope the residents are car people ), I can wind out 1st gear pretty well, but soon after I grab second it detonates pretty good, to the point where I have to either shift or let out. I realize regular unleaded has it's drawbacks, but if it was fuel I'd expect spark knock through out the whole range and not just when the engine is pulling in second gear.
My current tank of fuel is regular unleaded spiked with what was left of some premium no lead.
Could ignition breakdown be part of it? I have an MSD 6AL I'm considering putting on if for nothing else but the rev limiter.

Fuel pressure

I don't have a FP guage hooked up permanently in the car, I just have one to attach to the schrader valve on the rail so I'm not sure about WOT.
I'll check tomorrow what it is without the vacuum line attached.
Can a stock regulator be adjusted?

From the marks on the balancer, I don't think the PO knew how to adjust the timing. I had to scrub it clean just to put a mark on "0"

Detonation

I had the detonation problem before this hot idle situation started up, and before I adjusted the timing to 13*.
We had a car cruise locally here a few weeks back, it was a warm day and I'd get the dreaded spark knock even when I laid into it in first gear. I topped off the tank with some premium, thinking I got some bad gas and it just about solved it. It never fully went away, which is why I wanted to check the timing anyway.
I just marked the 0* point on the balancer since I have a good dial timing light that I've used many times before.
If it was knocking at 5*, then yes, it's really going to hit at 13*, I might just put it back to the factory 10* today.
I also pulled codes again yesterday, everything is clear except for the air inject codes which I expected to get now that the smog is gone.
What can I use to clean the IAC motor with??

Update #2

Well I pulled off the IAC motor and cleaned it, even though it really didn't look like it needed cleaning.
Once I got it back together I let it run for a while and tried to disconnect it. The engine immediately quit, so the motor must be doing it's job right?

While I was there I reset timing to 10* and took it out for a ride. I couldn't get on it like last night but I didn't hear any detonation either. The motor also wasn't nearly as warm as it had been yesterday so I'm guessing that might have had something to do with it.
I'm still pretty sure this idle issue will crop up again if I go out and get it hot. If it does, can anyone think of what I might be able to do while it's doing it to help diagnose the issue?