High idle

Not read the whole thread but some of the vacuum pipes only use vacuum when the butterflies are open
Depends whether there before or after the throttle bodies
Same with others that are using + and - vacuum such as one going to waste gate actuator

check this out. could this be related. i personally dont think so. am i right in thinking its saying code 21. ignition signal circuit. i reset it and ran it for a while, made no difference. but code hasn't come back as of yet.