I assume the previous system had no venturi.  The RSA-5 is fairly restrictive and I have thought a number of times about implementing some ideas to improve the flow characteristics that would probably reduce the pressure drop by perhaps half.  Sounds like you are down about 10% in power - the compression drop (why would you lower the compression when changing the fuel system?  I suspect there is a reason) would account for a couple percent and the restriction of the throttle body would account for another couple percent, but I can't make them add up to a 10% loss.