The GTV V6 CF2 manifolds are the same as the 156 V6 CF2 manifolds anyway, with the exception that there is a lambda boss welded into the rear manifold just after the collector on the GTV V6, you don't need this if you are using the original 156 V6 CF2 ECU. 156 V6 CF2 uses just one lambda, (GTV V6 CF2 has two, one on rear manifold and one on front front-pipe). On the 156 V6 the single lambda sensor fits in the front section, just after the pipes from each bank merge together. I guess this is your current set-up if you are using the 156 V6 front pipes.
Presumably you have blanked the lambda boss in your GTV V6 rear bank manifold up already?
From memory the outlets of the exhaust manifolds are 2.125" so ideally you want front pipes made up that are the same diameter as this, then have them collect into a 2.5" system from there to the end of the car. It would be beneficial if the measured distance from the collector on the exhaust manifold to the merge point can be the same for both banks although this is difficult to do and still maintain good ground clearance. But I wouldn't worry too much, this only really helps the sound quality and torque at low revs (scavenging).
- UK's leading independent Alfa Romeo specialist with branches in Bedfordshire, Cumbria & Dorset
Wizard Exhaust systems available here
Tel: 01768 879 171
Last edited by Pud237; 24-10-12 at 16:11.