Abrupt Fuel Pressure Loss '98 Mustang

I have a '98 Mustang convertible with standard V-6 engine. I drove it for five years with no problems until summer, 2008 when I made a 400 mile trip. About half-way into the trip on the interstate doing 68 mph with cruise control, the engine abruptly lost power, and I had to pull off the road and shut it down. After waiting a few minutes, I started it up and it ran fine for about another 50 miles then it did the same thing. This time the "Check Engine" light came on. The error code was P0174, mixture too lean, bank 2.

Early on, it only happened in hot weather when temperature was in 90s but lately it has begun happening in all temperatures. I can often drive over 200 miles before it happens the first time but then it happens at intervals as short as 10 miles and as long as 100 miles. The check engine light frequently comes on and lists either code P0174, P0171 or both. I have a code reader and I reset it each time. I never have any other error codes.

I took it to a Ford dealer but they said they could only repair it when the problem occurred and it never happens on short trips. On one occasion, I did take it to a shop and they were able to force the problem by taking it on the highway on a very hot day. They had hooked up a fuel pressure gauge and told me it abruptly lost fuel pressure. They said I needed a new fuel pump at a cost of over $1200 but I decided to get a second opinion before spending that much money. After discussing it with another mechanic, he said it probably wasn't the fuel pump because they are not prone to random malfunction such as I was experiencing. But he also had no idea what could be the cause of the problem.

Bottom line, I get a lot of guesses but no one seems to have a definitive idea as to what is causing this problem or how to fix it. I am hoping someone will read this and be able to do that. Thanks!