Fastbikes76 gutted his cats, and fitted additional plates that threaded into the exhaust before the O2 sensors, to fool the sensors into thinking that everything was fine.
Not worried about BHP but had the car sounding the same for over three years and for £100 just want to try out a different sound, if I dont like what I hear I will just remove them
My (cheap) ones have a synthetic rubber sleeve, but it isn't tight, which is why I'll fill them with silicone before leaving them to the ravages of under-car life.
These new ones are thick cast aluminium , old ones were like yours a synthetic sleeve.which were crap