I know you have a stock tank.....my dads car this past weekend was shutting off down track.....around 1000'...he made 3 passes scratchin his head...tore the whole thing down sat night in the pits....nothing....then I said....you still got foam in this cell?...sure enough the foam had started coming apart and had plugged the outlet just enough that under full power it would run out of gas....
Took out the foam...good as new.....

Maybe there is a wayward piece of something in the tank?.....never know!