Other than that, your fuel probably has alcohol in it. It attracts water and then the brass starts to grow the crud you mentioned. When folks start rioting over the price of corn tortillas and suger they'll stop putting it in our gas. But then older big block engines run well on it and so do our gas engines. Put a good filter anywhere you want it as long as you have one. The paper filtered clunks are nice though, they are heavy enough to follow the gas around, but are limited to a 3 line system and they present their own set of problems.