yes i agree the problem definately is timming i had a v8 that a customer brought in with those exact simptoms after he tried to do his own tune up, but replace a part for the engine with that of a v6 and so he was getting more spark than he needed thus igniting the mixture with the intake valve open on some strokes and on most cylinders. mechanical timming will do this also but rarely run. check coil packs or the distributor timming belt and any sensors like crank/cam position, even a tps will affect advance on a distributorless system. good luck
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