Over three years old cars are not allowed, however from time to time government allows to clear these vehicles with a 30% fine on top of normal duties. Its risky if it does not go through, you will loose vehicle.
This duty structure is most up to date and Customs follow this right from the day it was announced.
Regarding the other taxes on the vehicles: Those taxes are levied after you register the vehicle in pakistan and has nothing to do with Customs, its more like a provincial tax policy.
I will try to simplify the duties sometime but no time frame could be given as I am temperarily residing in Dubai now. Once I come back to my home town, I will sort this out as well.
Thaks all.