Yep, air bound fuel line/hose, and can be aggravated by clogged filter or ethanol gunked filter.

Just fixed this same problem on my boat; would completely stall out at wot, usually only when hot, which probably made the line suck more air.

Strange problem indeed, but easy and cheap fix once isolated.

We're going to see more and more of this every year as the ethanol contamination couples with older rubber lines in vehicles/boats/lawn mowers, etc.

I replaced all my boat's fuel feed lines with alcohol-resistant...

Try going up hills backwards. It could solve all your problems.

You may have to revisit this again unfortunately. Most of us may have this problem sometime or another. You can thank E-10 gas for that. Ethanol is a powerful solvent in today's gas. It will dissolve 30+ years of in tank deposits and then let them gum up filters and carbs down stream. If you got to clean out your tank well, you may be free and clear. When I replaced the OEM fuel pump on my old '95 Dak, all kinds of BLACK gas came out of the old in tank pump.