Rough idle with clicking sound

I would venture a guess that you have a sticking fuel injector and cause is loosened carbon and sludge deposits. The change in fuel coincides with deposits being dislodged. Clicking noise would be caused by injector mechanism not moving smoothly (spring sticking, disc hanging up, etc.). Since the injector is not operating correctly, the cylinder is misfiring, causing rough running and loss of power. Switching back to previous fuel type may help, but at least one injector needs attention. You should be able to locate clicking injector using a mechanic's stethoscope or by placing a long screwdriver onto injector body, then putting your ear against the screwdriver handle. Factory manual procedure is to isolate misfiring cylinder by slightly loosening fuel delivery line at injector body, with engine running. A good injector will cause engine to stumble and run roughly when line is loosened. After loosening and confirming injector condition, tighten the fitting snugly, then move on to next injector. Test each one by one until faulty unit is located. Injectors can be rebuilt, but it is not for the novice. Better option is to buy rebuilt injectors and replace any which are suspect. FYI: unburned fuel due to misfiring will dilute oil and wash down cylinder wall leading to accelerated wear. Attend to this problem promptly to avoid premature damage.

I would bet that changing fuel filters and running REAL diesel fuel will eliminate this problem. Our engines after all are DIESEL engines. Anything else is suboptimal regardless of it's "benefits" to the environment.

"Not a total answer, but I have had the same issue as you, with the same fuel. I am 80% certain the issue went away after running normal diesel for a couple tanks along with diesel clean additive. Switched back to HPR and the problem has come back, bit it is intermittent. Again, can't be 100% certain as I will switch back to normal again for a couple months again, and see if it goes away and doesn't come back. There are many possible causes of this sort of problem, like vacuum leaks or faulty injectors/injection pumps.

Cars from 1983 dont have OBD....that didn't arrive until late 90's"

In Atlanta, Ga. on a cold day (24 degrees), I had forgot to plug in my block heater. I had to recycle my glow plugs eight times without trying to start the motor before I got the motor started. There was a lot of white smoke, like a low cloud and the car ran very rough. I only use diesel fuel but in cold temperatures the diesel will gel and either not move at all and the engine will not run or move slow and engine will run rough. After running for at while the returning hot diesel warmed the fuel tank and the smoke went away and ran great as usual. You may also have one or more bad glow plugs as the glow plugs help smooth the engine until it warms up. If you have just one glow plug not working then your motor will run rough until the motor heats up.