This 83’ 300DT has had this issue for years. Never could figure it out on my own.
Maybe it’s worse now after I redid the head? It idles great when just slowly putting around town. Only has this prob when braking hard.

Still shakes at idle after adjusting valves, injection timing, replacing fuel filters, purging the injection pump, having Greazzer rebuild injectors, new OFV spring, putting in Lemforeder mounts, adjusting the throttle linkage. What else is there?

I’d compression test, but it idles perfect when not being driven like an ape

Ideas?