I have a 1992 GMC van with a 350 5.7 liter TBI engine. When I start the van when hot, it will turn over but immediately die. It will start and run if given gas when hot. The van has no problem starting when fully cooled. I have replaced spark plugs and wires, fuel pump and sending unit, fuel filter, and the distributor cap and rotor. The van runs around 190 at the thermostat housing and does not have any other noticeable issues while running (I use an infrared gun to check the temp). What else could be the problem?