Thanks.
I assumed the 02 sensor was not going to be the answer on this vintage of a car, but it's costless to disconnect it and go for a ride...
The Electromotive is running the ignition only; not the fuel. I updated the software/system about 3 years ago to the then-current state of the art software, but the system itself is probably 10 years old(?)
The LM2 would be a nice addition, but it's a bit spendy.
At this point, the mechanic tells me he's dialed the judder out at cruise, it's only a WOT that there's a pause transitioning through 4000 rpm.
JP