03 Plate Impreza misfire problems
 

A friend of mine has an 03 plate Impreza WRX PPP. Its been running fine up until now when it developed a slight misfire on wide open throttle, dropped the boost to 10psi and lit the management light up on the dash. Changed the plugs today, replaced them with exactly the same NGK R Platinum's that came out of it, it still has this slight misfire but only on wide open throttle

It has dropped the boost to 10psi in the past but only when 95 fuel has been used, due to knock detection probably, possibly mapped for 97 fuel?

The cars done 33k miles and i'm not sure if the fuel filter has been changed yet, can't see this causing any problems though?

I've read a few things on here about the Neutral Position Sensor, could this be a possibly problem on this car? Its not a bugeye, shape after.

Just looking for a possible quick fix before it ends up getting plugged into the diagnostics to read the fault codes.

thanks

no one?

up...