Hi all,
Currently using a Further with a Mutron, Keeley Compressor, tubescreamer, and an old Boss Chorus run into a boomerang.  Anyone have advice on whether to run the boomerang in the effects loop or out of the main output?

Hi Jeremy, welcome to the board!
 
I don't have an instrument with an effects loop, and I've never used a boomerang, so I'm not much help; but my guess is that you would want the boomerang outside of the effects loop since the parts you would be adding to the boomerang's looper might need to be at different volume levels.