on an RS a powerflow would be a no no, they just arent exactly designed with performance in mind

have a cat back system on my vectra sri daily though, mainly cos it worked out loads cheaper than a standard centre section replacement and irmscher back box from vauxhall. sounds nice too.

lads at my local powerflow are good welders aswel though, so that helps, quality elsewhere can be hit and miss, iv seen other powerflow systems that look like nursery kids welded it with a fisher price 'my 1st MIG'