I have same car and year as op. BB delete and it sounds luuurvley. Loud.. Yes! But in a good way, the engine note type way not the cherry bomb way.
Not been on rollers but no feeling of any drop in power at all, I read a pretty thorough post on Zpost regarding pressure and what's happening by the time gas gets to the back box... No difference at all having no mufflers other than glorious growls, pops and bangs.
Important to mention though... Long journeys in motorways is hell, I'm used to it but just got back from a 4.5 hour drive from Hereford today and I'm shattered, I just knackeres you out being droney. I mainly drive back roads 95% so not so fussed