I had a similar issue driving on highway in cruise. Took it off cruise and turned off air, pulled off road and shut off. All looked good under hood. Stopped by autozone, got codes checked, all good. Put Seafoam in fuel. Figured wwater in fuel. Have not had problem since. We'll see how long it lasts
Last month, I did a fuel pressure test and only got like 40-45 psi. Fuel pressure was also dropping to zero psi in about 2-3 minutes.
When I checked my 2011 5.3L silverado, fuel pressure registered at 55 psi and held for a long time. So I knew then that something is wrong with the fuel delivery system. I went ahead and bought a new fuel pump module and fuel pressure regulator. I dropped the tank, pulled the old fuel pump and put the new one in half a day. Also replaced the FPR.
It has been running really running good after the parts replacements. It already has about 165k miles.
I did not read all the replies on here but had something similar on a 98 not too long ago. When you say bucking, does it feel like it is cutting on and off, almost like a fuel problem? I thought the same thing for months and it would not happen all the time. I changed filter, ran seafoam and other injector cleaners through it, etc. It turned out to be he coil of all things on the way out. I changed the coil and not a problem since.