Hi, I need some help/information regarding this error code. First time I've had the engine management light pop up in my 2008 wrx, checked cylinder 4 and found whats on the pictures. Car has a big loss of performance below 3k but at higher rpm car seems to be normal. I have no overheating issues, oil seems fine and coolant is good too.
Please can anyone help with advice. Seems to some kind of foam thats build up on the piston, other cylinders are bone dry, just standard carbon build up. I did put some molybdenum in the car around 2 month when I last changed the oil and filter.
The car has around 91k miles on the clock. No mods and is standard map 226bhp.