94 Jetta runs fine until car warms up then check

Check the injectors, as these are a electrical part when the engine warms they may fail, if you are familiure with your engine (i.e. fuel rail and injector plugs) when this happens (i would recomend somewhere safeto puill over) hop out and in turn unplug your injectors with the enigine stillrunning, if you unplug one and the engine tone/noise does not change you have found the culprit.