A lot of times they leak where the flare sits inside the fitting. Try using grease or teflon tape. I have heard that a lot of the new fuel lines leak now a days.
NO tape, grease or teflon paste is recommended, plus a nice set of LINE WRENCHES, when you use a "regular" wrench on these fittings they distort the tube nut, basically egging it, so it dosen't seal/contact the flare 360 degrees, so it leaks....once egged, the fitting cannot be repaired and it will always leak no matter how tight you tighten it
As far as sixpack fuel lines, I use FINELINES or RIGHT STUFF STAINLESS lines...zero issues if installed properly, I've done quite a few sixpack set ups using their lines
Mike
