Engine begins "bucking" when cruising at 55/60 mph.

check the spark plugs.they are probably worn very bad.2 of them are under the 2 coils,and 2 under the wires that come off of the coils.do one at a time,don't cross wires.be very carefull when removing the plugs,cause they probably been in there a long time. DO NOT STRIP,HEAD IS ALUMINUM!if you have never done this,get someone who has.i just did this on same car,very hard to remove.but pb blaster is your best friend.plugs were shot,very bad.if the plug tube wells have oil in them,get the oil out,and replace the valve cover gasket and spark plug tube seals,and wires.if the plugs are bad,replace with NGK,part #3967,or NGK,part #7090.do not re-gap.if you replace,get a 12 inch piece of 3/8 fuel line,put the plug in one end,and start by hand,screw in untill snug,then tighten to crush washer.DO NOT OVER TIGHTEN.