Are you talking about just cleaning the lines or the tank as well?
One of the best cleaners around for the tank and lines is Marvel Mystery Oil. BUT its cleaning action will absolutely and totally clog the filters and make life miserable for days/weeks if the tanks really need cleaning.
Frankly, I'm not sure I'd do anything if it's all working OK - I learned that lesson the hard way on my previous boat. After putting MMO in the tank the filters were clogging in 20 minutes of normal running to the point of shutting down. Put in a new set - clogged again in 20 minutes. WHAT A MESS! THis continued until I built a fuel polisher and "vacuumed" all the fuel through a Gulf Coast F1 filter. THe tanks/lines were like new afterward thanks to the detergent action of the MMO but it was not worth the time/hassle since the boat ran fine before I did it.
SO...my advice is to be very careful about "cleaning" the fuel system.