If your Land Yacht is anything like the Classic motorhomes with 454 engines you likely have 2 or 3 filters AND a booster fuel pump located some where near the fuel tank. Early on Airstream retro fitted the motorhomes with the booster pump due to issues similar to what you're describing.
So along with changing your filters you want to make sure your booster pump is working.
Sorry I can't help you with the exact locations of the filters. Just follow the fuel line and you should see one or two inline.
Air forums # 1674
1974 20' Argosy Motor Home
1974 31' Excella trailer (parting out, as of 4/1/2015 I have wheels, brake drums, windows & holding tanks left to sell)