Fatory setting is the screw should be flush at the sleeve's top (about 2.5 turns)
and break in method is (as read out of my hpi manual): 2 tanks idling with wheels off ground, 3-4 more tanks low to mid throttle never use full throttle during the break in and let it cool down completely after each tank. Also make sure the piston is at the very bottom of the shaft (BDC) during the cooldown (and try and store it like that). make sure it stays around 250 degrees and doesn't go over 265ish. and has white smoke coming out of the exaust at all time.

I broke in my .15 nitrostar in that way and it works great and has not let me down.

if you want you can get the manual [link=http://www.hpiracing.com/graphics/instr/engines/15101.pdf]here[/link]

I agree on that nitro is a disease thing. Started out with a $100 MT1 and $100 in gear (gas, starter etc,) and have pumped over $1200 in it this summer (bought 2 MT1's (upgraded one to a MT2), Savage, original RS4, and some other things)