sputters while idling down
 

hi everyone
i have a 86 rx7 13b na all stock. problem is while idleing down from about 1500 rpm it sputters never stalls although makes me worried :( what could it be

has new plugs
all vacum lines

i was thinking possible a stuck actuator but not sure if that would do it im new to rotaries any help would be greatly apprietced
thanks james