no and no and no and no to all 4 questions 🙂
the plugs are different so not a direct fit
the standard injectors are good for more than you running right now BHP wise
the only reason to use them would be fitting a supercharger but even then the let injectors are only useful to 270bhp
you could increase the fuel line pressure and get less duty cycle on the injectors but you won't gain much
change the fuel filter and bang a can of Forte Specialist njectorCleaner in 🙂