hey I have a reissue FL9 flanger that I bought 2nd hand a while ago .I like to run it in fornt of the amp not in the effect loop . but it messes with the tone when bypassed . Its not tone suck or killing highs . its like it is doin a very mild flanging when bypassed which sounds like an out of phase kind of thing . tried it daisy chained and on its own power and its the same but it's worse with other pedals in front of it . Its the FL9 for sure. as soon as I take it out my tone springs back to life I got it for a real cheap price a few years ago on ebay and never used it much till recently . I'm thinking i got it cheap for a reason . Can you have a phase issue with bypassed pedals in front of an amp ?