I would definitely recommend a fuel pressure test and a fuel sample. Let the sample sit for a while to let any water settle out. You can do this, if you want. Get a clean, clear bottle and get a hose that has a fitting for inflating a tire on one end. The other end can be open, stuck in the opening of the bottle. Turn the key to ON, let it squirt and turn the key OFF for more than 5 seconds. Repeat this 5-6 times, or until you collect about 1/2 of the bottle (8 oz is a good amount).
Next, have the coolant temperature sensor tested for resistance range when cold and hot. I suspect that this is the cause if the engine is actually running at normal temperature. Also, make sure the exhaust manifolds and risers are clear, followed by inspection of the thermostat.