914 won’t go past 4100 RPM

I recently encountered the same problem as you. The manifold pressure could not rise further after reaching 32, and the engine would vomit if I continued to increase the throttle. I contacted the maintenance company and asked me to clean the carburetor. After I cleaned it, the problem became more serious. The intake pressure could only reach 27 and could not be increased. I was confused recently and didn't know where the problem was. Seeing your post helped me find the direction, thank you.