99 gtp intermittant high idle

i have a 99 gtp with 181k on it and ive been having a high idle come and go while driving. sometimes it will idle above 1200rpm i am totally lost on what it can be. i have checked vacuum lines but they seem good. could it be intake gasket leak or iac? i need some help please.

Any SES lights?

P0171?

A way to scan the fuel trims at idle?

no scan tool but i did catch it when i borrowed a scan tool early this year. i already have a code of a 401 for egr valve and 507 for high idle when i caught it