If im using loops i like to use 3 or 4 chopped up to make 1 main loop.
i also never have bits of the same frequency playing on top of each other...
For instance...say u have a single clap hit in ur trk and a loop ur using also as a clap in it playing in the same position as the other..cut it out and the same goes for any other percussion bit playing on top of others....that way ul get it sounding clean and tight....it also disguises the form of the original loops used.

Saying that, id chop up regardless, as if u zoom right in on them ,90% of the time ul find that the loops are slightly out of sync and for me thats when u can tell a loops been used as it sounds like its just been plonked in there...loose and messy.
Just use the bit u want out of the loop and cut out all the rest.