sufian!
its ok, tune up can increase its avg, otherwise, nothin can be said blindly.
ahmedbila!
i'll be there at eid,(home own), so fix it and tell me thn 
amir shehzad!
clean up throttle body, thts all.
vizual!
tell me wts under the hood, gap of plugs, how much air intake bloked, etc, thn will able to tell u anything,
green!
this problem nrmally happens whe ur carburator is take in air, so i must first suggest check the small vaccum pipes entering and cmng out of carburator,, for this look for the same cultus, park with ur car and match the air pipes.
inspire!
yes, same with vitz 2005. but this problem never arrive if u have tuned up ur car properly and gas is finely adjusted.