Agilent GC6890N registers only a single peak and it is negative. After replacing the inlet & detector ferrules, septum, liner, gold seal, & gasket, along with clipping the column and cleaning out the copper line to the filter, I had one injection register very small and delayed peaks. The very next run is back to a single, negative peak. Leak test shows no leaks. We have never had negative peaks. The single peak is at - 50 uV.