Still seems like fuel starvation though. Have you tried bypassing fuel pump relay/controller if there is one. This is not the main power relay (although worth replacing with Durite one) but the one near tank located under spare wheel area as here. If present its loom connector can have positive and ground feeds jumpered to bypass temporarily as below.

[Linked Image]

Richard

2018 Roadster 3.7
1966 Land Rover S2a 88
2024 Royal Enfield Guerrilla 450
1945 Guzzi Airone