Hi, i dont think that the oil change had any effect on the engine stuff, unless you some how bent or moved the linkage to the throttle or the fuel injection. my best hint from your posting is that the motor runs poor at low rpm. if this is the case the points are bad, and for a couple of dollars you should replace the points and the condenser together. buy two sets and keep one set in the glove box for emergency times. a tii is very sensitive to points adjustments and may need some adjusting by dwell setting as well. as for the k-fish pump having an oil controlled portion it does not. the pump operaters on about 2 psi of pressure which is lower then the idiot lite threshold so this is not a problem. good luck e mail me with results. stone stone racing co phila pa 215.592.0265