97 2.2L P0300 code

OK, I'm new here, and am hoping someone out there can help me. I've got a 97 s-10 2.2L w/ 100,000 miles on it. It began misfiring on #4 this past summer. Took it to the dealer, they said head gasket. I said "no thanks." I took it to another shop, and the mechanic there got the same reading, but said that it probably needed a tune-up and as far as he could tell, it didn't need a new head gasket. Changed out the plugs, wires, O2 sensor, PCV, fuel filter, and it still wasn't running well. So, I finally took the plunge and installed a new head gasket. When we took everything apart, and sent the head to the shop, they cracked it and gave me a new one. Put everything back together, made sure EGR valve worked, etc... Started the vehicle back up and it began to misfire again. Hooked it up to the OBD scanner tonight, and got a P0300 code. Any suggestions as to what might be causing the random misfire in the engine? Also, noted that when driving on the highway, oil pressure is extremely low.

Any help is greatly appreciated. Want to keep this truck, but don't want to keep spending money on it.

Might want to run some injector cleaner through it.

Ran some cleaner in there before the replacing the head and gasket. Should I try the cleaner again? What kind is recommended?

make sure the injectors are firing. did you check the coils to make sure they were firing?

Lucas has the best fuel injector cleaner.You can find Lucas at certain auto parts stores.You just put a certain amount in.Do not go with the cheap stuff that is out there.Did you put cheap plug wires on?Cheap plug wires will do that.

I put on Autolite Professional Series wires, Bosch Platinum +4 plugs. When we put the vehicle back together, we re-routed the wires like they were and ensured they weren't crossed over. I've checked to make sure they were in the correct order from the coil to the plug, and that's good too.

take back the bosch plugs and get a set of acdelco plugs. bosch plugs are the biggest POS plugs made.