It is very possible you need a reverse motor from the erevo..
I'm not sure if these motors have any timming in them, if so this is the problem as one motor, the reverse one is not spinning as fast as the forward motor..
http://www3.towerhobbies.com/cgi-bin...?&I=LXVDT4&P=Z
the emaxx uses two forward 550s, but the erevo needs one forward wired and one reversed wired to run at the same speed..
both the emaxx and erevo use the same forward motor