Just recently added Iron Moutain heads and the Mikuni carb from BPS to my 3 year old / 550 hour 36PD. My stock speed was around 27+mph / 4000 + rpms with just me and gear. Down slightly from new condition. I was running the stock carb and Gecker filter and adapter which initially gave me a 150+ rpm boost coupled with a high flow exhaust. With the Mikuni, IM heads, DB8 style modded stock intake and Marshmellow exhaust I am running as much as 31mph @ around 4300 rpms by myself now with a stock prop. 4300 rpms trimmed out for best speed is all I have been able to get out of it as it is running way to flat with the wedges I added to my hull. Average 30+ mph depending on conditions and all in deep water. Not sure why the gain is as much as it is with only a 250 rpm gain but it is there. I can only assume I was not getting the power to rpm ratio that I am now. Valve leak???? Much better hole shot now and the best part is I can cruise around at 26-27 mph and 3600-3700 rpms with throttle to spare. That is what I got WFO all the time stock. For a first timer doing these bolt on mods I would say it was fairly easy as it worked the first time when I turned the key.
The carb is smooth and accelerates all the way through the throttle. There are no dead spots. At 3/4 throttle I can turn it up and feel the boat jump. Not so with the stock carb. Overall the motor feels stronger than I can ever remember it feeling. I have not loaded it down yet but I am confident that these mods have put me over that hump with the heavy hunting and fishing loads I sometimes carry in an already heavy hull. I believe that 32 mph is achievable with the wedges removed and a little more prop. My main goal with these mods were to be able to step and carry a decent load in the upper 20s. I have ran things basically as they were sent to me without playing with jets or anything else. I have only adjusted the air screw slightly. Thanks to Keith at SETX Performance for the package deal he gave me and answering my questions when needed. I think these mods were/are worth the money and would do it again. 
Now its time to explore the prop scene......