On Alfa number 15
AO Platinum Member
Join Date: Dec 2005
Location: United Kingdom
Re: 156 cf3 cats
The cats rob 5bhp IIRC, as the CF3 is 150bhp, the CF2 155bhp.
You can swap the whole exhaust from the manifold back, although you will need to modify the CF2 manifold to allow the lambda sensors to fit.
You can't just swap parts of the exhaust, as the CF2 and CF3 bits don't fit together as its entirely different.
My mate reckons he removed the internals of the pre-cats on his sportwagon, so that they were just empty tubes.
That should gain you a bit more power.
TBH though I don't think you would notice a 5BHP gain on its own.
You will never be cool driving a Vauxhall.