I'm so sick of having problems , in the last week ive realized that I need a new timing chain set, new shifter seat and socket, and now on the way to work today my 87 truck started doing something real weird. It would all of the sudden go real lows RPM's, and the truck would almost come to a stop, and then go back to normal for a few seconds, and then low rpm's, and so on for about 20 times. I got it up into my work parking lot thankfully and it even did it when it was idling, as soon as I'd gas it, it would go high RPM's like it should, and then jump down to about 1000 and then back up. I just decided I was too stressed out to even look at at right then and there. So when I get off work, I go and start it up and it starts right up and I drive it all the way home problem free. I have no idea whats going on, it was almost like it was running out of gas. my guesses are bad gasoline or fuel filter. what do you think? Thanks

 

Sounds like the fuel filter.