so i got my engine back together and in, but when i start it it jumps idle between about 400rpm up to about 2000rpm, i have a brand new zzp PCM in it and sometimes it will thrown a P0603 code? is this a PCM issue or something else? I know some people are saying clean out throttle body and I cleaned throttle body and MAF real good, they're spot less. Any Ideas or things to check? all vacuum line and plug ins are where they should be. Any help is appreciated!

Thanks, Kenny