I would deffinitely run the fuel pressure test first, and a little trick if it is intermittent is hook the gauge up (if you don't have one beg,borrow or BUY...lol)and run it up over the wiper cowl and tape it to the base of the windshield, so you can keep an eye on it when you are driving. If it is the fuel pump, the pressure will drop off when it dies. I will say though that this problem (when associated with heat like you said) is usually an injector shorting out. I'd run a resistance check on the injectors and see if one of them has fallen below 12 Ohms.