I bought my 81 zxt about a week ago and it have a real bad idling problem and would smoke on the freeway (oil burning smell). This morning, i went and look under my z and found out that the transmission vacum modulator was leaking transmission fluid on to my drive way. I went ahead and replace the vacum modulator and the idling problem went away. I also replaced the vacum hose that goes from that unit to the intake and found some transmission fluid in it. My z was sucking the transmission fluid to the intake that is why i have a poor mixture causing the car to idle real rough.