I have been fooling with some nitro cars myself lately. I know on hpi cars, like the firestorm I've got, the needle setting that comes from the factory or the "break in" setting is to turn the screws till they are pretty much flush with the housing. Make sure you have a GOOD glow driver, like the sub c rechargeable type, and a good quality glow plug, the one that came in my truck woudln't even fire, get a mccoy or o.s. plug etc. I would run more than 2 tanks through it for break in, before you start leaning out the needles, you will read 100 different amounts, some people say to run a whole gallon through it even, I'd run at least 4 to 5 tanks through it varying the throttle and not getting over half, run it 2 to 3 minutes and then let it cool off and run it again for the first couple tanks, a infrared temp gun is nice to have, you don't want the temps up too high during break in once it is tuned it ought to run around 250 degrees so you want to stay a bit under that during break in, maybe 220 or under and most of all, don't forget to set the piston at bottom dead center between runs, this lets the cylinder contract back down to size, if the piston is in the way it can't, and over time you will lose pinch(compression) The oldschool method of breaking the nitros in was to crank the thing and let it sit on something and idle a tank or two away, this is outdated thinking, it's better to run them some on the ground, do figure 8's and vary the gas, just don't floor it for the first few tanks what you want is to get the heat up just above the 200 range, and then let it cool back off this is called the heat cycling break in method
73 cr250m elsinore, 85 atc70, 85 250r flattracker, 87 250es bigred, 86 tecate, 2004 gas gas de300