Wat brand and how much ? Is it reliable ?
Bump: For afm & manifold , i'd try my luck with the chop shop. They r half the price and i don't think the your problem r related to the manifold as they r made of harden material . If they leak it would only be the 'gasket' which is sandwiched between the cylinder head and the manifold.
I've changed the downpipe about 1 year ago. Increased performance? Yes!!. Stop knocking sound?? Duh?. Nothing to do with that. But you would hear a v6 rumble sound when the RPM is between 1 - 2.5K. Maybe the rumbling sound would drown ur knocking sound, heheh..
Here's a pic of it.
that also effected? how much u replace?