I am using 7AFE. Before i had 5AFE in my Car. with 7A my CNG Avgs local is 210 and touched 240 once in Pindi ISB with 55kg Cyl.
In Petrol I easily get 14 KMPL with heavy foot.
With 5A my Petrol avg were 10 to 12 and CNG 170. S0 this 1.8 Engine not only is more quiet got more low end torque and better consumption.
7A got a lot of low end torque and it can easily beat any local car and you need better low end torque in city driving so this saves you gas and easy to drive.
check my thread of Corolla 98 Swap.