Apparently, Mahrez had a nose operation in his country to solve a breathing problem but City weren't sure about the medicaments used during the op.
Anyway, the actual data about City regarding distance covered, sprints, injuries do not suggest they are doped (more than the other teams). If anything, the data suggest that it might be Liverpool who are doped because thei star players are not rotated, run a lot and look indestructible.
The logic based on Guardiola having previos 20 years ago when he was a player is tenuous at best. Let's ignore the actual data which are (or might be) suggestive of drugs and concentrate exclusively on what happened decades ago. It doesn't matter whether City are 10th or 20th re: distance covered and sprints, they are most likely to be doped because Guardiola had previous? And Liverpool are not likely to be doped, no matter the actual data, because Klopp has no history with doping? How dumb is that?