Code P0300?

Hello, this vehicle has the older Fuel metering system, or better known as Spider injection. Do you see the Fuel metering system on top of the intake manifold? I'll post a picture of it. But it's not a conventional fuel injection system. It has plastic poppets at the end of each plastic line. And they get carbon on the ends and start to stick closed. Some scan tools can do a fuel injector balance test on this system, but the sticking poppets is most likely the issue. They all seem to stick closed or open eventually., Did you have any spark plugs that looked different than the others, either leaner looking or rich? Do you see the top of this metering system on the top of the Intake manifold?

There are also 2 different types of fuel filters that can be on the vehicle, I would change that out first, and if you find any of the new spark plugs you have put in that are still clean, showing no fuel is getting into that cylinder, then the poppet injector is stuck closed on that one. I have heard of some shops blocking the return line really quick and the pressure build up frees the up the injector on this system. I have never done it before, but I have heard of situations where it worked. There is also an updated Fuel metering system as well.