if its something busted on the inside ie 1 cylinder has dropped out youd be blowing smoke everywhere and its be breathing through the breather pipes on top of the rocker covers
do you have any of these symptoms? also oil pressure would be low and water temp high
it may be a knock sensor - causing ECU to retard timing.
have you tried replacing coil packs, ignition module, spark plug?
what do the spark plugs look like? is cylinder 6 blackened? ie is it not firing at all?