dear, this is not prob at all.
first of all dont compare the pick on CNG with petrol other wise keep your car on petrol thoroughly but the CNG is more economical therefore it is much popular.
and for your car, get it tunned from good machenic. i have owned Alto VXR and very awsome pick on CNG and i was also very much worried about this and after getting it tunned from my machanic now i am much satisfied.