First of all check battery terminals as if they are lose car would be totally dead even after starting and working on generator if battery disconnects car will turn off. Clean the terminals with sand paper, apply little grease to it and fix them back tightly.
Secondly i think air filter opens with bang due to Back Fire. That means timing is not set. get it adjusted from 3S dealer.
Thirdly Zetronics adv + emmulator would cost you about 5 K including other small items. You would also need to change Switch which costs about 2200 to 2800 Rs. remember to buy M096 model.. never go for M 094 as it may need alteration. You may also go for zetronics digital meter and switch. It is little costlier but new tech in market. You may slightly increase the GAS supply and your AC would stop tripping.
BTW without emmulator running SANTRO on GAS is just humiliating