If the engine won't rev above:. (1) 2,000 RPM there is an issue with the Electric throttle control actuator.
(2) 2,400 RPM there is an issue with one of the MAFs / or engine oil pressure
(3) 3,500 RPM there is an issue with the VVEL actuator motor / relay
The lowest cost next step is to get an ELM327 and a app (Torque or OBD Fusion) and look at your "mode $06" data. (assuming your scanner does not read mode $06)
Mode $06 is a series of tests that are run on your car as you drive it. It also has counters that can tell you if the car has misfired. I suspect you will find some failed items in the mode $06 data, and that is your first clue to finding out what the root issue is.
If the above is not for you, then take it to a shop and have them scan and print the mode $06 data.