FT2000 and TX

'allo,
I am using a FT2000 and have noticed that the TX power varies greatly over the 2 min cycle. The power appears to change with each change of tone. It can change from 5W down to 0.5W over the cycle.
Is anybody else using an FT2000 or has anybody else seen this.
I know that the FT2000 is very sensitive to the frequency of the audio of the input signal. (Even the type of voice).

I was WSPRing on 10m for many hours yesterday and received a few big signals, but no body received me.

Thanks

Robert F5VHN