Even though it's a late model engine, the HO generally refers to the 91+ Chrysler operating system. Personally I would treat it as a renix and leave it alone except for some minor upgrades.
high idle could be a vacuum leak or a sensor going bad. there should be some sensor diagnostics in the link in my sig. also in that link is Cruiser's MJ tips. do all of them that apply. it addresses most all the shortcomings and age-related issues with our old Jeeps.