QUOTE
Anyway, I find a solution, I will low the levels of the wav files by 1dB before encode to mpc.
Mhhh... you shouldn't really do that. That still doesn't guarantee that your files won't clip when encoded to MPC.
I think you should be able to prevent the clipping by selecting "ReplayGain Off | ClipProtect title/album based" in the MPC Winamp plugin, or by using
--gain 0 --prev (for title based ClipProtect) or
--gain 1 --prev (for album based ClipProtect) with MPPDEC.
I still find it hard to understand why 89dB average volume is "too quiet"...