my z28 at startup goes to 500 rpms then stays there for a few seconds then after that it goes upto 2000 then drops back dwon to 1000 and holds stedy the same thing happens when i goto put the car into gear could this be the optispark? I allredy have the newer msd one installed can i clean this or do i have to buy a new one if this is the case

 

Check engine lite lit? Check for vacuum leaks, clean out or replace IAC valve. Check EGR valve.