"Bucking" with '86 318 lean-burn

I have a 1986 Gran Fury with 5.2L/2BBL and "Lean Burn" feedback
carb. Occasionally, when cruising at higher speed, (typically around 75
MPH, but can happen as low as 45) when throttle goes from just above
idle to a little farther open, does several seconds of severe
"bucking" or surging. Troubleshooting has been: replacing carb with
non-feedback type didn't help. Blocking off EGA vacuum didn't help.
Swapping out computer unit reduced frequency of occurrence, but
didn't stop problem entirely. Disconnecting and plugging vacuum to
computer stops problem, but causes loss of power and open-loop, gas
wasting carburetor operation. Vehicle needs to keep lean-burn stuff on
to pass MD emission inspection. Engine otherwise runs well, passes
inspection with 1/10 allowable emissions. Alldata doesn't show any
TBs for this.
Has anyone else seen this sort of problem, or have any suggestion?

Wow. No one else runs lean burn anymore! Secretly plugging the vacuum
line and reworking the carb to run conventionally might fix problem. Or
perhaps you could fit EFI and a catalyst in your state, since there is
no more leaded gas anyway. Finally, you could convert to LPG...

On Mon, 19 Jun 2005 wrote:

> Wow. No one else runs lean burn anymore! Secretly plugging the vacuum
> line and reworking the carb to run conventionally might fix problem. Or
> perhaps you could fit EFI and a catalyst in your state, since there is
> no more leaded gas anyway.

And leaded gas has exactly what to do with an '86 *anything*, pray tell?