Fuel injectors could be dirty, means the fuel drips in instead of spraying in and totally kills mileage, along with some of the other stuff mentioned like a carbon filled complete upper intake and bad filters, as well as an old and clogged catalytic converter. Also I guaruntee you that since it lacks power so bad he revs the heck outta it in order to get anywhere. Mine did this as well (92) and if he has the 8 plug engine one of the coils could have bad points which whether or not the other coil is fine sets him to default of 10* BTC, the MAF is also a common common common thing for Ford rangers of that year. Bad o2 sensor could hurt it as well. Theres alot of things to think about, and for those of you arguing about mileage, it dont matter. When you use variation of the equation youll only change his mileage by 1-2 MPG maybe 3-4 but even a difference of 4MPG means hes getting about 12MPG and that is still rediculous for a 4 banger, he still has a problem.