Car: 90 Laser RS (4g63t if you didn't know)

When I try to cruise at a certain speed limit the car is doing fine for a few sec. to a minute then begins to hesitate... gets jumpy... feels like its rocking forward and back then when I give it a little bit of gas it goes away. If I give it gas I don't notice anything except here and there feels like a backfire. If its sitting while idling same thing happens here and there it backfires. Now I haven't checked the spark plugs but the wires looked to be new and their in all the way. I do have a replacement coil pack that I have to install. But I'm wondering what this could be before going into any extent. Don't know how long the car has been sitting and if its been driving a lot or seldom in the last few months. When I bought it, it almost at empty (gas wise) so I filled it up with 93. Could it be that its been sitting so long that I'll need to run a Fuel System Cleaner (pour the bottle in my gas tank)? Any help is appreciate. Its boosting fine at stock boost.

My quick question:
Whats the recommended gap for the spark plugs?

I don't have time to research it since I'm at work and I'll be working on the car right when I get off. Stupid question I know but the sticker is missing underneath my hood which tells you also my Haynes and Chilton manuals are packed somewhere in one of my moving boxes and I can't find them.