Ok..  almost have it completed.. .need to know if Im going in the right direction or am I setting myself up for failure.

I just rebuild the top and bottom ends of my 250.  My carb (TM34) was set back to stock config..  37.5 pilot, 6fp60 needle on middle position, 240 main, air screw at 2 turns out, airbox lid on, frame boot off, 110 at 32/1 R50, FMF pipe and silencer (new packing), boyesen carbon fiber reeds on stock reed cage.  Im in NE PA at @ 1000 ft

I can light it up and did 3 heat cycles for break-in, re-torqued, and started to cruise around yard at 1/4 throttle.  It seems to load up with heavy smoke. Now...

I cant seem to keep it idling.  I reset cable with slack, adjusted idle screw to adjust slide height to @ 2mm. and dropped pilot incrementally.  To keep it idling I have to keep the idle screw all the way in, the air screw at like 3-4 turns out.  I ended today at 27.5 on the pilot, 3 turns out on air screw, lid on and idle screw all the way in... it will idle decently for @ 1 min then cut out.  I restarted it and removed airbox lid.. not I could back the air screw down to 2 turns, it would idle consistent and would chug on for several minutes.  Smoke was still present but not as heavy as before. 

Im starting to grasp the concepts here but seem to be confused why my pilot is way below the stock settings. 

Need some help with this.  Thanks! 

Your carb sounds rich.  Here are some other possibilities:

1.  It may be getting fuel through the choke circuit becausse the choke plunger is not sealing.

2.  The float valve is leaking a little because the o-ring on the outside of the seat is bad or the needle and seat is bad.

3.  The float level is too high.

4.  You are using pilot jets that are not sized correctly.  A common problem with the cheap not genuine Mikuni jets.

5.  The needle jet and or metering needle is worn.  The needle jets give the most problem with ware. Replace it just to be sure.

6.  A piece of reed petal is missing.

  The slide being set at 2mm is not set in stone, it is just a setting to give you a starting place for idle speed

Mikuni and Keihin tuning manuals give the theory for the throttle positions vs the circuit that is responsible for supplying fuel at those throttle positions.  If one circuit is too rich or lean it will affect the circuits on either side of that throttle position.