912 ULS LACK OF POWER

2007 REMOS G3/600 Rotax 912ULS 750 hrs on the engine, 60 hrs on plugs

Engine will not develop full power.

I went on cross a country over the mountains, engine worked great. Got home, put in 10 gallons auto gas from local gas station that we always use. 92 octane no ethanol.

Next day did a normal run up, engine would not go above 4200 rpm.

Drained some fuel. No water, gas looked good (a little blue from previous 100LL fill up before the 10 gallons of auto fuel)

Replaced throttle cables, replaced carb return springs, replaced fuel filter, and balanced the carbs.

Normal run up. developed 5000 rpm+ on the ground. Took off, and at about 300 feet AGL there was an abrupt drop in engine rpm to 4200 rpm at full throttle. I Landed.

On the ground I shut down the engine, I let it sit for a minute with the electric fuel pump on. Started up, normal run up, developed 5000 rpm+ on the ground, but after brief taxi it would only go to 4200 rpm.

HELP. Bad gas (not likely)? Bad float?

EGTs are about balanced. Maybe 100 degrees hotter on right front.