I have a numbered (.pdf) drawing of the 450 (not 451) fuel system, and there is what appears to be an inline fuel filter somewhere between the tanktop-mounted fuel pump and the engine.
Replacement info: http://www.evilution.co.uk/index.php...179&men=Engine. It is a strange looking system with three fuel lines and I think it is for a diesel (The #20 "filter" is in one line; the #25 canister is in another, and the third line is straight through, which may be an injector return line.). I don't have the descriptions of the numbered parts, and if I did they would be in Russian.
But, it looks like M-B/smart has at least thought of it before.
Probable correction re #25: a carbon canister.