efi hijet 1000 surging at tickover

Forum: 

any ideas why it would start surging?.
only thing ive done of note is run some injector cleaner thru the fuel(approx 2 tanks ago).
she runs perfect apart from the surging at tickover(somtimes revs high at tickover instead)
any sensors i should check?.
also where on earth is the fuel filter located,blowed if i can find it lol.
thanks.