Fuel System Issue - Vapor Lock??

My car was spinning like a top since its 2023 major service, best it's ever run. Then last spring, after an hours-long, spirited highway drive across states (to a classics rally), it stalled out on the highway exit ramp as I came to a stop. Had been pulling strong all day with no problems. Fired right back up just fine, but it did that a few more times on slowdown between street lights as I puttered to my hotel. During the rally, it pulled strong all day, and then acted out again in the same way toward the end of the day.

Both nights, I figured it was low on gas, or the fuel pump was overheating, so I topped up the tanks and parked it overnight. The rest of 2024 was mostly short local drives, and I had no particular problems.

Last week, drove across three states to see family. During a spirited run on an Indiana highway, it just lost power at speed and died. I pulled over, finessed the clutch and coaxed it back to life multiple times, limping it to a gas station a couple miles away. I suspected maybe my gas gauge had gone bad, and I was empty, even though it said I had a half tank. So I filled up the tank; it took exactly 10 gallons. After which it ran strong again like nothing was wrong. This made me think that, for some reason, it's not drawing gas from the second tank?

Drove home yesterday, making sure to top up the gas when it got to the halfway mark, and it pulled strong as ever for 360 miles. Drove straight to dinner with family, and parked it, no problems. When I drove home afterward, though, she wanted to stall out at every stop sign/light, and I could barely keep the car running by finessing the clutch and driving slowly at high revs. Got to the nearest gas station and it took 6 gallons to top up. But even that didn't help with the stalling the rest of the way home. At a standstill, it would idle fine with the clutch in, or in neutral while revving, but it just wanted to stall otherwise.

I'm stumped; what does this sound like to the experts?

 

I realize I forgot to add the important detail that, when I unscrew the gas cap, there’s strong hiss of air (waaay more than usual), and this shutdown problem only occurs a) after a long hard run, or b) when the fuel gauge is showing half a tank or less.

We did a complete restoration in 2017 during which time I replaced all fuel hoses and steamed out the tanks. I store the car every winter with a good amount of gas stabilizer, so I’d doubt it’s a crud clog. The internal filter sock was like new then, and I think the external fuel filter was done during a 2023 major service.