HITACHI ZX350LC-3 ENGINE BOGS DOWN

Hello, I have a ZX350 LC3 (6hk1 eng.). The engine runs good. When I try to use the boom/bucket in any way especially two functions at once the engine bogs down , sometime almost to a stall, and it will also barely walk. Engine / turbo work good. I have replaced all filters.

I was told it may be a sensor on the pumps but unsure were to begin looking. Any help would be appreciated.

HITACHI ZX350LC-3 ENGINE BOGS DOWN