Reading Peter's post on the fuel lines reminds me about the Charcoal cannister.
When I had my tank out, I replaced mine, and re-routed the suction hole into the engine bay (normally sits in the frame in the left wheel well).
I put a small fuel filter on the end of the hose to catch any debris being sucked in.
Given the engine bay would have less dust than the wheel well, and I do not do a great deal off road, the little filter gets very dirty!!
If you still have an original charcoal canister, it's sure to be blocked by now, and will affect the breathing system of the tank.