Kendall:
you will be pleased with the DSII ZX21,i dont use the breakin bench,what i do is mount it on the car and run two to three tanks (rich)and then i finish the process on the track with atleast three to four more tank while i start to tune in this process,i found that its the best and most consistent way for the life of the engine,hope this helps and dont hesitate if you have any doubts..
Roniel
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SERPENT USA/MEGA/JACO/PMB