hello!
yeah you must thanx your Vti for the 1st won...air blocked on CNG and timing advanced....i am sure ur car was knocking like hell na...have you notice?....advancing timing on CNG means over advanced timing on petrol...not retire...resulting in early ignition so early pickup but low end power....
anywAYZ...get bigger engine..install CNG and run it like hell :P.....
Thanxxx