99 Suzuki DF9.9 Backfires thru carb

[Gary B]

My 99 Suzuki DF9.9 four stroke backfires thru carb at about 1800 rpm and will not go above 2600 RPM. Items done-Cleaned carb, adjusted float several times, replaced fuel line and tank, fuel pump, coil pack and plug wires, plugs, CDI unit, disconnected neutral switch, water pees fine, not overheating, adjusted valves (do not appear sticking), sea foam 50/50 deep clean, timing advancing OK 5-30 degrees, and compression is good. Other than pulling the head and checking valves I am at a standstill on what it can be. Any ideas? Thanks.