Well, I got my valve stem seals replaced earlier this fall. Just this past week, my '84 SR5 developed a slight sputter under load, like going up steep hills. It's not bad, and hasn't affected the fuel economy, but it annoys me. I first replaced the plugs, distributor cap and rotor. Since that didn't help, I replaced the fuel filter (should have done that first at $3.99 from NAPA). Still the same deal. I'm thinking since the gas mileage is still the same (35 on the highway, 30 in the country, 28 in town), might be fuel delivery. So I just put my backup carburetor on. We'll see how that goes.
Does this sound like it could be a valve clearance thing? I was very careful and believe I set them right, but that's the only thing that should have changed. Idle is fine, so I don't believe it's a vacuum problem.