Yes, I believe that is true for a lot of 166Mhz-equipped PB1400s. While information exists on overclocking lesser speed 603e CPUs in a PB1400 however, there is no info out there for the 166Mhz part. You could always experiment with this though, going off the link below:

http://hardsdisk.net/1400clock.html

... I'd love to know how to speed up mine. I was never a fan of the PC1400 due to it's sluggish speed, but did find the first release of WinAMP for Mac (called WinAMP!), let me play MP3s without skipping doing other things. Nothing else worked well enough.

JB