SC chugging?

i was driving on the highway for about 20 mins when all of a sudden my car started to chug, maybe buck is a better description, and the tach started to dance around. I put it in neutral and checked all my gauges, all fine. put it into 4th, still chugged when i gave it a little gas (just when the boost gauge goes into the 10 area for vacuum.) so i babied it to my destination, let it sit for about 10 mins and started it up...no problems. i cant think what this might be....fuel pump maybe? any ideas are appreciated. i have recently replaced, fuel filter, fuel pressure regulator, crank sensor, and cam sensor. thanks! btw its an 89 5spd

Most likely the cam sensor. I went through the same problem. They are about $32 at Autozone.

i already replaced the cam sensor

On my 90 SC, it ended up being the crankshaft sensor (ONLY after joining the sccoa did I find out what it was, thanks guys and sccoa).

Check to see if the head of the crank bolt is still there or if the crank pulley wobbles any while turning.
These are sure signs that you need a balancer (REAL SOON)
On mine, the balancer was fine but it looked like every now and then the sensor and vanes were touching.
--Fred

probably fuel pump mine would do it after it warmed up like you said about 20 min sometimes it took a couple hours a lot of times it would be ok until i slowed down or stop . finally after about a year of trying sensors i put in fuel pump and it was fixed