Ok problem is solved, not the easiest solution but it works for me.
The pod is set to "ABCD" mode to switch amp channels with FS5 - FS8, and change the presets.
In every preset I have a "dummy fx" assigned to footswitches FS1 - FS4. I only wanted Preset 1 and 4 with fx loop, so I assigned the FS1 and FS4 with Midi Command toggle CC85 Value 127,
and the other ones with toggle CC85 Value 0. So pushing FS5 enables fx loop, pushing FS6 disables, and so on.
I tried 4cm, and now this wiring to have a no coloring, clean bypassed sound. And in ervery method the sound is coloring. Not a lot, but audible.
So I'm happy now.
Maybe the newer Line 6 stuff like Helix HX or other ones have a better bypass,so you can always play fx on, but this things are hard to find used in Germany.
Thanks a lot.