Anything's appreciated here: I've got a seasoned '87-'93 5.0 that starts up great, idles well, but after running it around the block a few times, begins to sound like an old-time tractor... kind of "putting," if you will. Give it some time to cool down, start it up again, and it's fine. Run it around the block and we're back to the tractor effect. Any ideas? *I just replaced the dist. cap, rotor, plugs, and wires. It uses a PerTronix ignition module. Vacuum may not be absolutely optimal due to some old, bad lines. It did this before I did the plugs, wires, cap, and rotor.