Pre-cat bypass vs. secondary cat bypass

[backman_z]

In a previous thread, the topic of secondary bypass pipes came up. The Radium King (a forum member) suggested the following:
“i think, from a flow turbulence reduction point of view, that it is best to have the restriction as far down-stream as possible. in the case of the Boxster, this means deleting the pre-cats (the ones on the headers) and keeping the secondary cats (the ones on the mid pipes).

so, it would be less expensive, and provide more power, to get a set of those cheap Chinese headers on eBay (they come without pre-cats and are designed to connect direct to the mid-pipes) and keep your current mid pipes. this will require some post-cat o2 sensor kung-fu, however, as you have to either (a) extend the sensors to after the secondary cats (and perhaps add a bung) (b) get a ROW flash so that your car doesn't throw an emissions code, or (c) get one of the many o2 sensor simulators or 'foolers' such as sold by fvd (or fab your own).”

I vaguely recall reading something about bypassing the pre-cats in another discussion. I read about secondary cat bypass a lot. I wanted to bring up discussion in another thread to find out more information. Has anyone done this? Can anyone verify that one is any better than the other?