I had a car that did this. Replaced the accumulatro and check valves, still exactly the same except pcoket heaps lighter. I then decided that, because it started more easily when I put my foot on the gas and then when it did start blew a little black, rich smelling smoke, that it could be the injectors leaking down. I replaced them and it fixed it 100%.
Symptoms were,

-Hard to start when hot and left for 15 mins or more (if I restarted before 15mins it would start fine)
-Started quicker if I helpd my foot on the gas.
-No problems starting when cold.

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Andrew
300e 294,000mi
380sel 185,998mi
380se 309,980mi