MIL is on. DTC P0300, P0304
Chased spark and is not coil, plug, or signal sent (ckp)
The problem could be a blown head gasket or also a clogged cataltyic converter.
Does the car overheat? Troulbe starting? Check your coolant level and also the engine oil level. Check oil for contamination.
For the cataltyic converter you can take the car to a muffler shop and they can do a back pressure exhaust test.