I have an exhaust leak between my downpipe and tubular o2 housing. I went to buy a gasket and when it came in they also had an exhaust manifold gasket. They tried to say I would have to replace both to do a proper install. I helped a friend install a downpipe onto a stock o2 housing and we didn't do this. I've never heard of replacing both. You can just replace the one gasket, right?

 

What is a Tubular O2 housing? Do you mean aftermarket O2 housing or a tubular exhaust mainifold.

Your post isint clear as wher your leak is at. It will be two gaskets if its at the header.

Only one if its at the downpipe.

Block/header/O2 housing/downpipe

 

i tihnk he meant the o2 housing to the Dp. get an Doughnut gasket. iot should fixed the problem

 

The leak is between the aftermarket o2 housing and downpipe.

A 3" donut gasket, correct?

 

that is correct...but it wont make a difference in performance

 

Ya I know. I can't let air from outside into the cabin of the car without dying of carbon monoxide poisoning at this point

 

If you find a 3" donut please let me know.

People say an exhaust leak at the DP doesn't effect performance but to me it looks like it does. A leak effects back pressure. Maybe I'm just paranoid.