For anybody wanting to try a twin rear setup, here is one i knocked up yesterday.
So, in this example, im keeping the centre muffler, adding a new flange about 200mm behind that muffler, and bolting this onto it.
First thing was to replicate the original bumper cutout to the drivers side.
Its all 2.5" parts... flange, single to dual collector, all 2.5" mandrel bent tube, a dual 3" tip on each side.
under the car, it clears the breather canister but require removal of the other part that vents into the chassis and rerouting of the pipe that fed it.
Noise level with this setup is a bit too much in my opinion, but my partner says its ok. i find it drones too much between 1500-2000rpm. A bit like a didgeridoo.
but anyway, i just made it as a trial... will try adding a 12" long glasspack resonator before each tip later. will need to relocate that canister first tho.