2000 Mustang Gt manual transmission 109k miles misfire P0300
I bought this car at 106k miles and I haven't had any issues till a couple weeks ago when I got a check engine light, I scanned for the code(innova 5160rs) and got p0300 I checked the spark plugs and I found that the gap was wrong so I gapped them all to .053, the code instantly went away after I started the car up and I hadn't had problems since, then I got the same code again recently after stopping at a different gas station than I usually do I used up most of the gas then stopped at my normal gas station and I deleted the code, it didn't come back for awhile but again it came back what could it be?
The code is saying misfires on multiple cylinders so it will be helpful to determine which cylinders are acting up.
On your Innova 5160rs go to the cylinder misfire counter and take a look.
If you see misfires on all the cylinders, clear the counters and then see which cylinders act up 1st.

I don't know if it's because my car is older or my scanner needs an update but I don't get the option for misfire counter
Worn out plugs, coil pack, injector. Switch the coil pack to another cylinder and see if the misfire moves there. Check continuity thru the spark plugs and grounding electrode wear.