Where is the computer pin connector to hook up a diagnostic computer

1988 is still OBDI and you should able to see a plastic receptor (like a computer plug in) and you should be able to get simple flashing lights on your dash that are going to give long & short flashes like morse code. If you google OBDI you'll find a youtube display or two on the generalities of what to do and you should be able to find an OBDI code list. Every car is different so I can't point to where the plug is on your car nor give you the specs on your car. Mine idles around 550 - 650 , but I run at 700 cause that's the way I like it. Shop manuals are the place to get specs but they are expensive, I've found free owners manual web sites but I have not been able to find a free shop manual ( where they didn't ask for too much personal info.) Sometimes you have to bite the bullet and buy a shop manual when you are interested in knowing the actual specs on your particular engine. Hope someone reading your question has one and will share.