I dont agree with u. This car also has a MAP sensor.
I have the same car running without advancer for quite long time but whenever I try to run it on petrol it gave knocking coz the distro was advanced to get proper idle and pick for cng. But the day I installed advancer, not only its CNG average got alot better but also the knocking on petrol ended too coz idle get set for petrol and car advanced automatically on CNG.
Therefore I suggest u to install advancer for ur car too.