1992 318is wont rev over 3k rpm when warm
hello everyone. i am new on here. I have a 1992 318is manual trans with about 191k miles. About 2 months ago the car would not rev past 3k rpm when the car warmed up. it would do this is every gear and even at idle. I replaced the cpu, the mass airflow sensor, the cam sensor, the fuel prssure regulaor and smoked the intake with sea foam twice. I also put in a new o2 sensor. i also took off valve cover to see it the chain stretched and it was fine. None of this helped. i did a search on google and it appears that this car is notorious for this exact problem. no one really puts what fixed it though. some said it was the cat, or mass air flow. i cant disconnect the cat to see if it revs when not on car casue the bolts are to rusty. Anybody have any clue what this could be,. thank you in advance guys.