E28 Acceleration?

[Mark <mrich22@xxxxxxxxxxxxxxxx>]

    I'm puzzled at this point, and wonder if anyone has any advice.  I
have an '84 528e (manual).  When I am cruising at say 55-65mph and let
off the gas, instead of smoothly decelerating, my car tends to drop-back
suddenly before leveling out.  I'm pretty sure that there's something
preventing a much smoother transition.  If you take your foot of the
gas, shouldn't the engine maintain a smooth decline, rather than this
distinct drop-off?  Any clues or recommendations would be appreciated.

------------------------------