Vibration rejection MPU-6050/ITG-3200

Hello
Could anybody tell me, what can be wrong, when gyro output is very fast drifting in low frequency (output) while electric RC helicopter is running (1500-3500rpm main rotor, motor cca 10000 - 40000rpm)?

I working for longer time on the software vibration filter, I need good latency (max ~8ms) and better filter characteristics than internal low pass filter.
Commercial products with IDG 500 and ISZ 500 can filter out ALL vibrations except resonant frequency with no drift. So I guess MPU chip should be more vibration immune.
I tried FFT low pass filter which can filter out nearly all vibrations, but it is filtering to cca 30Hz, lower frequencies can be from RC model movement during flight, so I cant filter it more.

Following graph is with FFT filter while motor is running (DLPF 256Hz):


Next graph is from model movement without powered motor:


Testing RC model is very good, with as less vibrations as possible so on cheapest RC models it can be much worse. You can see, I have to filter out low frequency vibrations with amplitude bigger than classical movement. While I want to make own filter, I configured gyro for 256Hz/8Khz filter.

Following graph is from powered motor with only one dimensional kalman filter, it is cca 3x better than internal low pass filter configured for 42Hz:


Somebody know, how to filter out these vibrations/drifting?
MCU is 32bit STM32.

Thanks