You do it on the main straight with the HS needle set very rich, to the point where the engine sounds like it is going to die, but not letting it go on to 4 stroking, and since you are operating on the main needle, the low needle is away from the spray bar so more fuel and air goes in, and actually lubricates the engine more, so there is no problem with damaging. Remember very very rich 2 stroking, not lean WOT, Leave that to when you've finished Break-In and are tuning for performance.

AFM