you said you isolated the area but i think you should consider this. I have a 99 v6 and i had that same set of symptoms. look at the AC Compressor clutch while the engine is running. if it is bad it will lock and you will have a significant noise like a wine. as the rpms increase it will get louder and if you turn the ac off it is just annoying. as for the smoke yes that is how i discovered the problem turn off the ac with the engine runing and rev the engine. look where the pully is there should be a large amount of smoke surrounding it or pouring off of it. hope this helps. it cost me $250 to fix but i had it done under the counter ford charges somewhere around 5-6 hundred. im pretty sure thats your problem my friend who fixed it for me is a certified front end specialist for ford in Kansas and he said that was a very common problem with the v6s. good luck.