I just installed a Picco Max .21 in my Revo and have to say that it was very easy and straight forward. I have put Three tanks of fuel thru it and have to say that i am very happy with the power compared to the TRX 3.3. I am still getting it tuned but it is much snappier and has much more low end compared to the 3.3. I think once it breaks in completely and I get the tune right, it will haul ass.
I am happy with the ease of installation and the performance of the Picco Max .21.