That is why I post this to bro. RENESIS
Driving pass 4k rpm is rich air/fuel ratio, probably add more carbon....lol
Drive constant 100kph on highway, I think 90kph even better ratio for a longer distance will clear carbon better. My wife SUV after an outstation drive she always comment the SUV have better and smoother drive...
Can 80kmh in 4th gear work? Drive for around 25 to 30 minutes.