My car has some problems with the engine. When the right throttle body is unplugged, the left side would work well. When the left throttle body is unplugged, the right side would work well. However, with the boths sides plugged, the engine cannot rev past 1900 RPM. What should I do?
Your engine has gone into "limp" mode. The engine computer senses that one side (or the other) is performing inadequately, which causes it to shut down that side. This is most commonly caused by fuel pump(s) failing. The fuel pump assembly should be replaced by a professional mechanic, like a certified technician from YourMechanic who can come to your home or office.