1995 Cadillac Deville Fuel grade

I just bought a 95 cadillac deville with a 4.9 fwd and she has a bit of noise coming from the motor not to sure if bottom end or top but im thinking the previous owner had ran low grade fuel for awhile and I just put 15 gallon of low grade in it before I seen it was premium only do you think it would be fine if I ran some octane booster with the 15 gallons then switch it back to premium to see if it clears up? It is also a tad bit hesitant but doesnt stall. Also would a low/Weak battery cause it to throw codes and the heater or blower motor to work only sometimes