Stainless exhaust design one silencer per pair cylinders?

[wrongwaysurf]

Hi guys, bit of help / expertise required! had a new stainless exhaust made up by power flow franchise for unmodified 2.1 Ss petrol. They suggested Splitting the system so it runs in parallel so each pair of cylinders feed into their own silencer and tailpipe, said it would improve performance and be quieter - bonus! Well it ain't quieter but it sounds pretty good I have to say and has a lifetime guarantee. Does anyone see any major flaws with such a design? It run great apart from the odd misfire running downhill in gear ie engine braking. They were reluctant to fit a lamda probe but I would like to have fitted it , obviously now it will only be sensing the output from two cylinders if I have it retro fitted , is that better than nothing? Ok so I guess it wasn't the best design after all.........Can anyone help with the Lambda probe issue? I might fit it anyway and see how it goes!

Thanks