White Smoke at Idle on WVO ('81 300D non-turbo)

I've been running WVO for three years without too much smoking. Now I have lots of white smoke at idle and low speeds after commute home from work. I've noticed this only in the evenings on my way home and not on my way to work, even though the conditions are very similar. This started a little after replacing the injectors with Monarchs that were professionally pressure tested. The other correlation is the recent onset of cold temps around 40-50F. A few other pieces to the puzzle:

• Valves are adjusted (once per year)
• Diesel purge once per year - usually flows clean
• New VO and diesel fuel filter
• VO is corn oil that is filtered to 0.5 micron absolute and dewatered
• Diesel engine always has run on the cooler side, barley reaching 170F, even though I've replaced the thermostat several times. VO reaches 120-130 on freeway and 130-150 on arterials. Would like higher temps.
• Air filter could be changed, but is not really that old.
• No loss of power noticed.

Any suggestions on getting the smoke down?
Thanks,
Rusty