I haven't heard or felt any difference between regular and super in the '84, 
but I sure have felt the difference when they add the winter methanol for CO 
reduction in the winter.  It was particularly bad with the BP gas, but a 
tank of Chevron or Texaco cleared up the problem.  When I lived in Colorado 
they added MTBE (ether) to the gas for the same emissions reason and we had 
no problem.  Bottom line, octane is not the only issue.

Charles Vaughan
'84 GL (Texaco 87, Chevron 87, BP 87 summer only)
'88 Nova (92 octane required to not ping, any brand)