88 Pickup wont run for long
 

So I have an 88 with a 22re in it. It'll run decent for about 15 or 20 minutes. Im guessing this is time for it to warm up. Afterwards it'll lose all power for a second and then get it back for a second and so on. It'll do this until it completely dies and then it is a bitch to get it started back. It'll do the same thing once I get it back running. If I let it set for a while it'll start right back up and go. This started maybe a week ago. I don't know much about these trucks besides this one is being an ass. I'm thinking maybe the afm or o2 sensor could be the culprit?

When idling it also idles around 550 rpms and it surges up and down somewhat

Idle surge, intermittent loss of power, stalling.
This could to be the signs of a malfunctiong TPS
Do you have a multimeter so you can check it?

Before you throw any parts at it, I would get a Factory Service Manual and do some diagnosis.
I would definitely check to see if there are any stored trouble codes.

There are. Code 21, 24, 31, 51 and 52 lol

Have you done any work on it lately?
That's alot of codes stored at once.
What I would do is clear the codes first and see how many/if any come back.
Your going to need a FSM to diagnose any codes that return.

http://www.4crawler.com/4x4/CheapTricks/TroubleCodes/

There was one in the tool box when I bought the truck so I have that covered. The fuse trick doesn't work because I've already tried it. About how long do I need to leave the negative cable off?

Time and temperature go hand in hand. If it consistently shuts down or runs crappy at a certain time, suspect a temp sensor. I had a water temp sensor in a Honda that failed, but still within the realm of possibility. So the car thought the h20 temp was about 20* when it was 70* outside and would crank open the IAC raising the idle so it would eventually stall out. It would do this the same distance from my house repeatedly. After it cooled it would start right up. Time = temp.

That actually makes a lot of sense. I will try that and get back to you. I drove it around the neighborhood for about 20 minutes but I might not of got it warm enough. I didn't get it out of 3rd gear