I had the silencer and second cat deleted a couple of weeks ago. Fast road conversions did all the pipe work. Custom made s/s pipe work with sensor fitted aswell. He angled the sensor so it's in the exhaust diagonally. It keeps the EML light off as it doesn't catch a lot of the emissions
It spits, pops, bangs, crackles, farts and it'll probably make me a cup of coffee if I ask it nicely. It's going back to FRC for a remap though as that flat spot is noticeable.
It doesn't happen if you keep the car above 3000 rpm, it happens between 2500-3000rpm ish. It's only for a second or so. If you're booting it, you won't get it as the revs won't drop enough. If you're in second/third at low revs you'll notice until it picks up.