first timer need help.

First time on AF hope you can can help.
Have an 1995 Sonoma automatic v6 vortec and just recently my rpm's have been jumping around on me by 200-400 increments every couple of secounds. My truck will do this when idling or driving and also makes the truck feel like a rocking motion when driving. I thought maybe and fuel filter so I replaced that but nope didn't work. I don't have an scanner and the check engine light isn't on.

Does it feel like engine or does it feel like transmission?

have you pulled plugs out and look at them? my dad just bought the same truck for my sister and same moter as yours it has 275000 mls. on it and runs great. have you done any thing else to it? because sounds like a plugs or plug wires. if you don't want to pull plugs try some sea foam in it. but i would pull plugs anyway and see what they look like. and if you replace plugs i would put ngk's in it.....good luck..

wow thanks for the wuick replys well lets see i replace my plugs to bosh platium 4's about 2 years ago they are still good and it feels like the engine not the trans.

Check fuel pressure and leakdown rate. Ignition in RUN position, engine off, fuel pump running, must be 60psi to 66psi. Pressure must remain above 55psi for 3 to 5 minutes after the fuel pump shuts off. Use AC Delco plugs ONLY! Anything else, you're asking for trouble, and you'll get it, guaranteed!