Not sure if the car was always this bad (or if I just got a really bad tank of diesel).. but it seems to be smoking a tad more than it used to. The color is grayish white (If I recall correctly). Though, I'm not too sure on that. It's enough to notice it when on the highway at night (I can see the smoke in the headlight beams behind me).. and enough to barely see it at WOT from a traffic light. Idling in a light wind, I can sometimes see a little smoke wisp away.

The engine doesn't burn much oil, though it does leak quite a bit from the oil filter housing (where it meets the engine). End up putting about 1.5 quarts in every 3000 miles. Blow-by isn't serious (at least, I dont THINK so).. it does have the "smokestack effect" when removing the filler cap, but aside from vibrating the cap very slightly (moreso due to engine vibration, I think), doesn't blow it off or anything.

Any suggestions? Diesel purge it, or put in a fuel additive? Not sure what to do to stop the smoking. Fuel filters replaced about 6000 miles ago, air filter about 8,000.

Diesel purge is always the first and most economical choice.

If an injector is clogged or the nozzle is bad, the fuel will cause this type of smoke. They need to be pulled and tested on a bench for spray pattern. As these engines get towards 200K, odds are good that one, or more than one injector are not up to par anymore.