If you really think that great surface area Volvo filter that actually does filter, is choking the B23 and limiting it's raw power potential, try running without a filter and seeing if you can tell any difference, aside from the placebo effect. Try a drop of snake oil in the tank too while you are at it.
On the other hand, GRM magazine added one to an old Porch and measured before and after and did claim to register a small improvement. Personally, I do not believe in them (oily, porous filters) but people will believe a swear by the weirdest things, I have learned. Death to extremists and you know who I mean.