i am using 3rz fe hilux tiger 2002, it gives average of 9 to 9.6 km from lahore to murree. Dont push its not a sports car its smooth moving engine.
For bad fuel few points first is your engine dual coil or distributor, now check plugs, plug wire set try using genuine or good one, get your throttle body checked as loose butterfly leads to bad fuel if so get it fixed, check your airflow sensor and vaccum set.
these engines are good task performers i have managed deosai with no issues at all in same fuel average.