Let me give the whole story. I have a code that says high RPM detected. I changed the IAC, TPS, New timing chain, Cleaned the EGR, new plugs, wires, distributor, rotor, cap, Crank position sensor and it still shows the code. It runs great except for at a stop it rough idles for 3 - 4 seconds and then is fine. During the rough idle, the oilpreasure gauge is going crazy and then it goes normal

 

Have you verified that you have no vacuum leaks? An unlit propane torch works great for this. With the engine running, trace along all vacuum lines and the various different interfaces between components with the torch. If the idle increases or smooths out, you've found your leak.