I believe it is more likely to add more fuel when the engine is cold (or the ecm thinks the engine is cold). The 24 lb injectors, however, will cause it to run rich unless you have a 93 cobra ecm OR a maf that's calibrated for 24lb injectors. But in all those cases, the car should still start and run. I would start with the basics. Warm the car up and then shut it off. Try to start it. If it won't start, check for spark...then check for fuel. Easiest way to do this is to spray a little shot of ether in the intake and see if it fires. If it does, then you're getting spark, but no fuel. If it doesn't, you can suspect a no-spark issue. This test probably won't really tell you if you have a weak spark or low fuel pressure, so keep that in mind. Either way, I would suggest keeping a fuel pressure gauge around. You can buy one for about $20 or so and it's money well spent.
Some common problems that occur after the engine's warm: ignition parts breaking down under heat (tfi module, pickup coil in distributor, the ignition coil). Fuel- dirt/gunk/rust in your tank which gets sucked up into the strainer sock on the pickup tube, dirty fuel filter, weak pump
These aren't the only things that could cause your problem, but they are all common issues with these old mustangs. Engine management parts can also cause some problems. Dirty maf, dirty/faulty iac valve, dirty throttle body, bad 02 sensor, temp sensor (there are 2 of these...one for the temp gauge and the other for the ecm). There is also an intake air temp sensor, but to be honest, I think it's more for fine tuning the fuel mixture. I've never had an issue with mine and currently, it's literally just zip-tied up underneath my upper plenum. Car runs great as-is, so I don't mess with it lol! Just about every other thing I've mentioned above has broken or malfunctioned at some point in my 88gt and I've only owned it a few years.
One more issue I can point out is with the fuel pump relay. I've never had an issue with mine, but I know it's a common problem. I don't think it would be affected by the engine temp, though. Same with the ecm relay. Usually not an intermittent problem.