HelloCustomerand welcome to justanswer.com,
When it stalls what are the lights on the dash doing at the time?
Does it happen when the car is warm?
How many miles on the Element?
the temp guage in the dash has no relation to the engine temp which is controlled by a separate sensor in the engine compartment. The fuel pressure may be ok but you will need to have the injectors checked to see if maybe one or more may be leaking over night causing a load up of fuel overnight.
When you replaced the plugs did you use NGK original equipment plugs?