On the inside of each header there are 2 round bosses that appear to be welded in the middle. Does anyone know what they are for? Do they go all the way into the inner port? Reason I ask is I would like to drill and tap one for my wideband O2 if they go all the way through.

Here is a pick of what I'm talking about.

Computer and shifter bracket mounts.
Allen

Thanks, Allen. but those are the smaller ones that are already drilled and tapped. I'm refering to the larger ones to the left and right.

Thanks,
Frank

Frank -

Might have something to do with the casting process ?? Drill into them and you might hit water, might hit exhaust. If you do drill into an exhaust port, it would just be one port. Don't 02's like to be at the collector, read all 4 cyls ??

Can you put the fitting in the tail pipe?

Put mine in the tailpipe by the flange. Work fine. The only area I think you will find a solid aluminum wall to the exhaust is down by a port on the first three inches or so. I don't think I would be drilling into the area you mention.

Thanks for the input guys. Right now I have it in an aluminum spacer I made that goes between the tail pipe and header. If you look close in the first picture you can see it. I was actually just curious if I could move it a little farther down, but it doesn't seem to be getting wet like I thought it would.

Frank