Mike,
I'm sure both of my Saito's are real close to being the same rpm's at full throttle. I ran them without this system hooked up and they did well. One of the engines (Master) has a little richer run up so this is the only reason I dedicated it to being the Master. The Slave engine has a flawless run up. Both of my engines were used with new rings and bearings. I just about have them broken in now. They are the older version with larger fins.
I can't say enough about the EMS/Jomar Twin Sync System. It works and does it well. I can fly my twin with confidence that both engines will be turning up the same rpm's and I won't have to make inflight adjustments on the rudder to keep it straight.
Perry