1996 400 Immediate Stalling After Start-Up

[LS4hunnit]

Okay here's as in depth as I can go about the problem. Was on my way to work and the car was beginning to overheat (been having radiator problems - got those all sorted out though), but it did not fully overheat, maybe about 3/4 the gauge, maybe a sliver more. Parked the car at work for 8 hours, got off, and as I went to start it she immediately stalls. I don't get the chance to gas it or anything. Here's what I know and what I've done:

Has spark - it's starting up and turning over fine - just an immediate (I'm talking like .5 seconds of run time) stall

Replaced the radiator and gave her a coolant drain/clean (old one snapped on the upper outlet due to bad coolant/age)

Replaced fuel pump, and I can hear it surge every time I turn her over

Replaced fuel filter - old was was quite nasty.. but not the problem

Replaced MAF as I was reading here that can sometimes cause the problem

Now my problem has not changed one single bit. I figured next I'm going to give my IAC a good cleaning, make sure it's not getting stuck. How about the coolant sensor? Would that cause the problem? I only ask because the last time she ran she was a bit hot.

A side note.. ran an OBDII before I changed the MAF (got one from Autozone that gave diagnostics reading, not a code) and the only two that came up were MAF and Air temp control. Upon speaking to the guy at Lexus, he informed me there were the same unit. Now, my dumbass didn't have the MAF plugged in when I ran the OBD.. so i plug it in and everytime now i just get a "synch read error" or some bullcrap telling me to turn the key "off" wait 10 seconds and turn it "on". I'm losing hope but will see what happens when I clean the IAC. Thanks in advance