I just got a new to me Mazda B2500 truck. 1998, 4cyl/5spd, 2wd, 238,000. It runs great, but took 4.5 gallons to go 60 miles. So far one of the coil packs has been replaced, all 8 plugs and the plug wires. What else? O2 sensor? I'm going to pull the air filter too. The truck runs fine and has plenty of power at all rpm.

Any ideas?