I have a 2000 v6 mustang with a manual tranny. A few months ago I had a really shake from the engine and turned out to be the harmonic balancer, of which i replaced and i solved the issue. a week or so later i started getting misfires on cylinders 1 and 5. read up on it and changed the tone ring on the balancer which fixed the misfires on those cylinders, however the misfires instantly went to cylinders 3 and 4. I've replaced the coil pack, all spark plugs and even the camshaft synchronizer still no change. i did do a tune up 10,000 miles prior with everything. its no gotten a bit worse and i just am not sure where to go from here except into the engine.