i dont think any of the areas are 100% Pashtun. There will be quite a few non-pashtuns from nwfp most notably hazara there as well as people form punjab sindh and muhajir backgrounds.
the Pirwadhai area of Pindi has a large pakhtun community not sure if its 100% or whatever.
There are entire colonies/places in Karachi which are 100% pushtoon. Can anyone tell me a single one from Rawalpindi?