Whats the benefit of using the 2wd exhaust manifold over the 4x4 one and would i also have to change my downpipe?

any help would be grateful and wheres the best place to take my saph for a health check and tune , i'm in scottish borders

cheers stu

 

The 4wd one allows for earlier/quicker boost but ultimately limits the power compared with a 2wd one, I'm most likely going 4wd just for under bonnet space, earlier boost.
tabetha