They used to have a vacuum diagram under the hood of the car. Or you can opt to just change out the vacuum lines that you can get to - as vacuum lines are pretty cheap. I agree with Dave, sounds like a timing/vacuum advance issue - usually if the car run perfectly fine but sharply deteriorates when the engine speeds increase, this is almost a sure sign of the vacuum advance not working. Could be as simple as a loose vacuum hose, could be more involved, depending on what happens from that.
That said, there are a number of things that could cause the symptoms you are describing. Could be a dying ignition coil or intermittent power getting to the coil, excessive ground noise (ground loops), wrong gap on plugs/incorrect plug temperature, clogged fuel filter, dying fuel pump, bad fuel pressure regulator, clogged EGR, bad vacuum modulator, induction leaks/obstructions, exhaust system leaks/obstructions, lazy or dying O2 sensor, burt valves, timing jump, bad pickups in distributor, etc.
