98 Mazda B4000 5spd stumble / engine balance

129K miles check engine diagnosed by local Mazda as miss fire on cylinder #1. I replaced fuel filter, MAF (junk yard), 4 plugs out of 6 replaced (other two this week due to angle), replace all spark plug wires and an oil and filter change. On idle it feels like the engine is missfiring (I have spark on all wires as I tested at the ignition block via one wire at a time. The seems out of balance on acceleration. Ideas ?