Weird engine hesitation and stuttering after warmup?

When I first start up my truck, it runs fine and accelerates fine for the first several minutes. It even seems okay for a few minutes after the coolant has reached the normal operating temperature.

But then the engine will begin to slightly stutter, almost imperceptibly at first, and gets steadily worse… jerking a bit while I’ve got pressure on the pedal.

It’s not the transmission. I can reproduce with no load on the engine, the transmission in neutral.

At first I was thinking it might be the fuel filter… but I’d expect that to happen all the time, not just after warming up.

Maybe the spark plug wires? But again, why only after it’s warmed up?

I do run premium fuel all the time to prevent spark knock that occurs, especially on warmer days.

I’ll probably take it into the shop tomorrow for evaluation. What should I expect them to suggest? What should I be wary of?

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2000 Nissan Xterra XE
3.3L V6
4WD, manual transmission
115k miles