they changed one plug wire? why not all of them? did they change the spark plugs? also whats the mileage of the trk? did they change the fuel filter? dd they check the fuel pressure of each pump before the fuel filter or at the fuel rail? ok heres what i would do ifi was you, make sure your tune-up is good. make sure you have new spark plugs,wires,cap,rotor button, fuel filter,air filter and pcv valve. if it has over 100,000 miles go ahead and replace the coil, but when your changing the spark plugs look at them, see what the tips look like, that will tell you a lot, also just go ahead and check the compression while your changing your plugs that will tell you if your having any type of cyl problem as well