well.. it all depends how much money u r willing to spend in your AE71. You r probably running with a 4A-C SOHC.. I will personally go with a late model low milage 4AGZE engine. This engine makes 165HP stock.. is basically a 4AGE engine with a supercharger that powered the late models of the first generation of the MR2's. You can get one of those engines with trans, ECU and Harness for $800-$1500 in Japan.. i dont know how much would it cost u in PK.
You also have other more modern options like a 20 valve 4age gray and black top, a VVTI black cover 20 valve 4AGE or a good old 16 valve 4age that for pakistani should be a racing engine.. DOHC, 1.6liters, high compression rate and EFI of course.
Dont get a carburated engine.. they r not efficnt and obsolete.. is like buying a musket when u can get an AK47 for a little more money.