Salam.
Non Custom Paid(NCP) Cars, jeeps, suvs bla bla. are vehicles that a) entered Pakistan illegally b) Custom duty hasn't been paid.
They are usually driven with fake number plates- LRZ 786- Tindoo's SUV.
Chassis and engine number is tampered or copied from an accidental car. Some cars have identical engine number and chassis numbers.
You don't even know if there is a car with same details as yours, you could be in Lahore and other car could be driving around in Islamabad:P
Customs officers are on the look-out for these, especially in Punjab and Islamabad etc. If you live in Quetta and areas near Afghanistan border, you can roam around in them freely. NCP cars aren't really welcome on PW:)
One of the ways to smuggle one;