Have a 20hp Briggs long tail. Has a rev kit, 35hp carb with K&n filter which was tuned by ec carburetor and a dual exhaust. I run 4600ish out of the water. First time running ot after the mods and in the water I'm only 2600rpm. Actually gain 150rpm when I run it choked but it is also sputtering a bit when I do that. Any advice?