Won't Rev Past 2000

[Hook0076]

So a while back, my 2003 2.0L, manual gearbox started to kick and buck at 2000RPM and wouldn't stop until I passed 2500RPM. I neglected to look at it until one day it stopped at 2000RPM, jumped between 2000 and 2500 and refused to go any higher. It threw 2 codes, "Air Intake Tuning Valve" and "Camshaft Position Sensor Circuit". I replaced the CPS and checked its connectors, but the problem continued. I reset the codes to see if I had eliminated at least 1 problem, but it threw the CPS code again, only the one this time. I was told that it could be an EGR valve malfunction and the car is using the CPS as a scapegoat. I unplugged the EGR and ran it again. No change. It will sometimes break free of the 2000-2500 lock and I can get it to 6000, then it stops again. Any pointers to finding the problem? Thanks

[1Mazda323Fan]

Need a little more info first. How many miles on the car? How's the idle? Any weird noises or smells? It does still start, yes? Right now, I'd lean towards a problem somewhere in the wiring to the CPS, the timing belt jumped a tooth or two, possibly an obstruction in the exhaust? There are a few things it could be, but if we get a little more information we can help narrow it down some more.