I know it say's that the FXi has already been broke in at the factory but take my advise and run at least 4 full tanks of fuel thru this motor before you start leaning it out very much. Of course I'm talking (on the ground) running. Both of mine started running like they should after several tanks of fuel was burned. They were much easier to adjust and now run very consistant, starts easy and smooth transistions from idle thru WOT on take off's and most importantly "in the air".
Yeah it's messy with the fuel all over everything but it's easier to clean the plane than repair broken balsa from a deadstick landing.
It's just my opinion and take it for what's worth to you, these are fantastic engines if you run them in correctly before you put them in the air.