89 GT 5.0 KOEO test shows continuous memory codes 18 and 96. The engine mainly only stumbles while trying to maintain speed on the road with minimal throttle, but seems to lack some torque under full throttle as well. The engine revs smoothly, and steadily holds at any reasonable RPM when not under a load without stumbling. Base idle is set around 600RPM, Base timing is at 14deg and TPS voltage is at 0.9v. Does anyone have any ideas on this? She's drivable, but just barely while maintaining speed.