IAC valve ka masla... Cultus's kabli parts are rare as it is a veryyy old discontinued car in the world and Baleno's throttle will not fit in. Thats why Cultus's kabli parts are expensive and rare. The ones you find are actually out of pkdm cars repaired and refurb. The throttle body plus IAC sensor of my Liana is available readily in market for 2k total! If you can spare some time, i can accompany to shafiq mor market tomorrow morning to arrange something for your cultus..
However, iac and throttle ka koi taaluq nahi missing se. So missing wala mamla alag hai... I am scared for your case now
There could be vacuum leaks, improper fitting/sitting of gasket and imperfect sealing