Very intermittent stalling
About 2 years ago, I had two occasions of stalling at highway speeds. Truck would start bucking harder and harder until it quit completely after 10-20 seconds. After letting it sit for 5-10 minutes, it started up and ran just fine. About a month later, the exact problem happened again. I couldn't pull any codes, didn't see anything noticeably wrong, so I just chalked it up to bad gas or temporary gremlins.
Same issue happened about a month ago, then a second time a few weeks later, same result both times. Then today, it happened again, but after restarting, the truck would only run for about 30 seconds before dying again. This happened 3 times in a row and then I was finally able to make it the 15 minutes home without further incident.
I did the easy fix after the first time today and replaced the fuel pump relay without success. Fuel filter is only 2-3 months old, so I don't think it's that. Never have a problem with starting. I use good gas (or fuel additive/cleaner) every so often. Wondering if I should look at replacing the fuel pump, or if there's other things I can check before going through the hassle of the hard fixes like that.
The weird part of the problem is its intermittancy, and I'm wondering if that may be a clue to its cause? Anybody have any ideas?