1995 Buick Somerset car stalled

1995 Buick Somerset mileage: 86,000. My car was running fine until it stalled going down the road. It wouldn't start back up until it cooled for a little bit. It runs fine until it gets up to operating temperature. Then it stalls, and won't restart until it is below operating temperature. Previous owner did not properly care for this car and we put a lot of new parts into it. Like: ignition module, plugs and wires, alternator, starter, fuel pump, fuel filter, transmission fluid and filter change, battery, water pump, serpentine belt, PCV valve, coolant sensor, oil pressure sensor and speed sensor. This car has a digital dash with all the gauges. When we did the first oil change, we got a small amount of sludge after draining the oil. Two weeks of driving 85 miles a day to work and we did another oil change. This time we got a bunch of sludge and my husband figured he should flush it out. He used a can of Motor Flush and got more sludge out than we thought we would. The intake manifold is just as bad as far as carbon build up. We used a can of Prestone Air Intake Spray and it seemed to run smoother. However, it still had lots of gunk in it so he sprayed it again to clean more. A few days after that is when it started stalling as soon as it got to operating temperature. It doesn't matter whether it is sitting at idle or running down the road, as soon as it gets to temp it dies. We just replaced the oil pressure sensor and now when we start it, it reads 2 bars and drops to nothing on the gauge. The oil indicator light does not come on at any time during idle or road driving. It doesn't show any codes on the computer either. We are totally stumped. Could we have dislodged enough sludge to plug the oil pump screen? Or, could some of the carbon worked its way into the injectors and plugged them up? It runs fine until it gets to operating temperature though. What are we missing?