The Italian job was done when it was driven from phoenix to palm springs faster then average by a driver friend. The engine is not hitting the body through a bad mount. It feels like an internal engine thing. I am leaning to injecting systems but am looking for a pointer. It feels like it could be an out of balance crank but unless that was changed I can't imagine it just going out of balance by itself. Also it just look like the engine has been out at all.

I am still chasing this shake down. If anyone has more help I'll be glad to try.

Did you follow up on the previous suggestion about the rack dampner ?
That was built into the system to help out after some things got worn or loose..

Some thoughts come to mind,..

If you are having this issue when you accelerate, it may be that the banjo fitting on the intake manifold is stopped up. If so you will not be getting the boost signal to the anoid telling it to increase fuel delivery in concert with the additional air. You can check this by getting a 1/4inch tee and some 1/4 poly,.. place a pressure gauge in the signal line at the anoid. When accelerating at an on-ramp, I may see as much as 9psi boost, and cruising at 65mph, around 2 psi boost. That is on a car with 330,000 miles on it.

The rack dampner, I believe only comes into play at idle. It supplies some tension/support to the injection pump to help smooth the idle. The service manual says something to this effect, " to minimize longitudinal ossilations ", adjust the rack dampner.

Also I had a associate whose 300D ran rough at times, and would also top-out at about 60mph. Found the small screen style fuel filter extremely dirty. It was clogged to the point that if you tried to raise the primer pump, it would suck a vacuum to the point of prohibiting a full stroke on the pump.

Good luck