Thanks to this and several other posts on this subject which helped me tremendously. I thought it only fair to share my success and methods to maybe help the next in line. My 94 LS400 started blowing puffs of white smoke on start up and continuing to do so while at idle but not as bad. After reading many posts, I decided it was either the air control valve (idle control valve) or one of the coil packs. I bought both parts. Air control valve I got for $80 at a toyota dealership (part# 17630-16040) and the coil pack was $39.99 at Autozone (part#C903 i think). Got home, pulled plugs on each side to check for unburnt gas which would tell me it was the coil pack. All plugs looked fine. For those who haven't pulled the plugs before, they are in the middle of the valvle cover. To get to them...remove the plastic piece towards the front of the engine, the one between the valve cover and the intake and the one running down the middle of the valve cover.(this is for the driver's side, passenger side is the same but you must also remove the air filter and tubing leading up to the engine) You will need a 10mm socket for most bolts, a 5/8 spark plug socket, and a 17mm wrench for the air control valve.
The air control valve can be located from pictures on various posts. I found it by following the two small hoses leading from the intake down to it. It is screwed into the bottom of the power steering pump below the power steering pump resevoir. I first tried to access it from the top only to have a difficult time and almost started removing the power steering pump resevoir. Don't bother with all of this. Take the large plastic under belly completely off with the 10mm socket and access it from the bottom. Find a short 17mm wrench and a good light. BEWARE...fluid will pour out on you when you get the valve out. It covered my right side.. =) Lovely feeling at 2am with work closing in at 8am and no sleep. Anyhow, the valve is a simple unscrew and replace then replace the rubber hoses. You might need pliers for the hoses, I pulled them off and reattached with just my hands.
PS. I knew it was in fact the air control valve as when I removed it, the center piece creating the valve close off fell out and there was fluid in the hoses leading to the intake.
Good luck. Hope this helps the next person.
Nikk