Has anyone had problems with fm reception. Before fitting the previous head unit was fine

I dont have the AR3 (x5500bhs) but I've had the same problem as well. With the stock head unit or the z110 I had before this unit reception was perfect. I think it may have something to do with the HD radio installed in these newer units and the antenna setup on my vehicle, I dont have an actual 'antenna' on my car so that may be my problem (Its one of those 'woven into the back window' antennas). Plus it doesnt bother me as much as it's probably the least used source by me.

I have the AR2 and the FM reception is poor compared to my stock head unit.

Some stock hu's have an antenna amplifier built in.  VW comes to mind.  A relatively inexpensive aftermarket antenna amp should fix you up.