steelies are heavy but on the same time they are more resilient and provide rail like driving experience with properly balance rubber on them..
alloys are light weight as compared to steel rims and look good on car, hence might very slightly improve the performance of vehicle both in terms of fuel economy and initial pick up..
however as mentioned above its really hard to find new quality alloys matching with mehran OEM wheel profile, however many options will be available in chinese alloys which are before par quality mostly...
sub standard alloys are not only heavier than the steel rim but also very weak... they are prone to breaking on impact rendering major damage to car while the steelies might survive with a bend...
heavier wheels also do affect the suspension of car and would be needing earlier expense to overhaul suspension...
however you might try your luck finding a used set of very good light weight alloys having profile under 5% range of OEM but concerns are it shudnt be repaired and perfectly balanced...