This sounds like mass air meter interference. If you have an exposed air filter in the engine compartment this would be the cause. The air pressure waves (aka fan wash)from the fan will disrupt the air meter.
The air meter, being the largest part of the computers fuel equation, determines how much fuel is required (indirectly) and when its signal is disrupted it will subsequently "lean out" or "go rich". Hence the bucking is caused by the "lean" condition. This happens so fast it appears to be a miss but it is not.
Simply place a piece of cardboard or similar device along side the air filter to block the air flow path from the fan to the filter. This is a high tech problem with a low tech solution.
Mike
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