Ford Repair: 93 ford escort 1.9 shutter, vacuum leaks, ford escort

Question
The car has been tuned up, plugs wires cap etc.fuel filter changed. ran code check said running too lean, changed the o2 sensor, still get shutter 55-60. let off gas speed drops below 55 it wil then pick back up.

Answer
Lean can be from one or two things. Fuel related, lack of. Usually due to a clogged fuel filter, or low fuel pressure. Look for vacuum leaks around the throttle body and intake. Carefully spray the intake, around the injectors looking for a change in engine speed.