My thought on the pump is the unknown abrasiveness of that dust you found in the filter, long term wear on the pump thoughts.
Sounds like they hire Can do type contractors to get site work done.

Cheers, Charlie
If It ain't broke, Modify it!
87 Montero turbo Converted back in Spring1989
95 Montero SR 3.8 DOHC Only one?
93 Pajero 3 door 6G75 Mivec with paddle shifted 5 speed
Then a Gen2 SR with full coil independent suspension.