Can someone explain what is a 2 step secondary rod tip?

 

Sure. Most secondary rods taper down to a certain tip size and then hold that tip size out to their end. In other words, it's the same sized tip from, say, 70-90* of air valve opening. However, some very rare secondary rods ramp quicly down to a certain diameter tip and then have another distinct step down in size at even further air valve opening. Like it'll be a constant .056" from 70-80* and then drop down to a constant .051" from 80-90* of air valve opening.

They're pretty rare and the oddball step-down doesn't seem to make a big difference in tuning EXCEPT you must be sure how far open your air valves are opeing to know if you ultimately end up on the first or second step of the tip at full laid-out WOT.