I have a 07 with DBW Stargazer and z-box. I also ski behind a 2012 Nautique with ZO. Both systems are set at C1 and I am trying to get through 28off at 34 MPH. I am not a good enough skier to be able to tell the difference in the pull characteristics between the 2 boats. Certainly not enough difference in the pull characteristics for me to want to pony up the extra money to put ZO in my boat. I spent a lot of time and effort getting Stargazer dialed in (see my thread about this on this form) but after that things for me are fine. The throttle versus DBW issues have been discussed at length in this forum so that part of the egn should be fixable. As everything in life I can only tell you what I have experienced and thus let you judge the relevance to your situation. Trying to save you money is all this advice is trying to address. BTW Do 04 Responses have throttle linkage set-up for PP? If so how does this get replaced with an ECM? I had an o5 Gekko that was throttle PP so don't know about Malibu's of that age. Also from the link above @Markchilcutt posted in there:
"There are no calibrations for any 2006 Malibu Boats for the E Controls ECM. Although 2006 boats had MEFI 5 and DBW there does not seem to be the will to release an ECM for this model year. I guess if enough people created the demmand it could be done. Zero Off needs an E Controls ECM,CAN wiring from engine to dash, Drive by Wire Throttle and the ECM calibrations to run the boat."
To me this all sounds like lots of money. Hopefully you can find out it's not if that's the route you decide to go.