I have an issue with the engine wanting to stall out when it is cold, and sometimes when it is warm. The idle is a tad rougher than most SR's I've experienced and overall the car struggles to get over 20 MPG. It drives fine apart from a partial throttle surging issue when I'm under about 3000 - 3200 RPM typically when the engine is warming up (read: not cold, but warming)

The car has a new 02 sensor, relatively new ignition components (rotor and cap look decent, no build-up or burning), plug gap is normal (whitish - brown tint), reground MAF, removed EGR, removed AIV, engine doesn't appear to be sludged up so I believe it to be in good shape, doesn't burn oil.

Sometimes when I start it to go home at work the engine will run on 3 cylinders. Application of throttle brings the 4th online but it will go back to missing as soon as the idle comes down.

I'm thinking it's either an injector issue or a TPS issue, something else that comes to mind is crossfiring on the wires, but I have given it the pitch black test.

most likely its your injectors or spark plugs. while its running, take off each spark plug wire individually and see if the engine changes. if you find your bad cylinder... then go from there. check the spark plug, take out your injector and see how dirty / clean it is...

I think I'm going to just replace the injector o-rings, one might be leaking a bit under high vacuum.

Before you start replacing stuff, check your ecu for codes. It should tell you the problem. You can take it to a dealer, or do it yourself for free. Here is a link:
http://www.sr20forum.com/showthread.php?t=96214&highlight=coolant+sensor

Nissan's Consult I sucks at giving off codes, my 02 voltages were all over the place causing the engine to run rich at cruise yet I get no codes. If this were an OBDII car I would have gotten the code.

Thanks for the advice, I use the Consult computer at the local Nissan to diagnose the car since I know most of the people there.

Do the power balance test.