P0300 2003 Infiniti G35 -

Question

P0300 new spark plugs and intake gaskets, car has poor idle and acceleration

Answer 1

If you are not using 91 octane start filling up from Shell and use a good fuel system cleaner and do an intake flush to decarb the engine.

could also be 1 or more clogged injector, ignition coil and so on

if the car is burning oil I would do a compression test