Is the duration around a second? Is it at a certain rpm? Under light throttle? My '92 does something similar once in a while, accelerating lightly at 1800 rpm going through 45mph. I have a badly leaking EGR pipe but other than that have not been able to determine what causes it. I cannot repeat it consistantly, which does not make diagnosis easy.
It is very short like you said around a second or less. I can not pinpoint an rpm but under light throttle is correct...very strange