Exhaust issue

Sounds like you're talking about the exhaust pipe if its connected to the exhaust manifold

This is the exhaust pipe that connects the exhaust manifold to the catalytic converter. Sometimes it is reffered to as a down-pipe. It is made of steel and the rippled look is from bending it around a curve. If you get headers or high performance pipes, they do not have these ripples and are smooth. This is called a Mandrel Bent pipe and its smooth surfaces allow exhaust to escape faster which increases performance.
It is not an easy pipe to replace. You might find that you have to lift the motor a little bit to get it out. To do this if you need the room. First jack up the car and use jack stands to keep it up without the aid of a jack. You should be able to shove the car around and be assured it will not fall. Get a flatt widee piece of wood to put under the oil pan that is big enough to support the entire surface of the oil pan without denting it. With a jack, put just enough pressure on the board to hold it in place, remember that you could possibly lift the car off the jack stands when performaing this operation and that would lead to a dangerous situation with the car unstable on the jack stands. Find the reaer motor mount. You might find that you do not need to completely remove it or you might remove another component to get the pipe out. At this point it is a good idea to soak the exhaust pipe nuts and bolts in either WD 40 or PB Blaster. Do this at regular intervals and wipe it off in between and it will make a world of difference, sometimes all the difference, in removing the exhaust bolts.
If you do need to remove the motor mounts, loosen the bolts and apply a little more pressure as needed to the jack to remove the bolts and remove the mount. Leave the jack at this point and replace the mount as quickly as you can, even if it is going to sit while you get another exhaust pipe, by putting it into place and putting in bolts just finger tight.
Exhaust nuts and bolts can really be tough too remove as they rust quickly. When removing them, stripping one or breaking it can mean a lot more time to fix it, if you can get in there to fix it, and/or more money to buy more hardware to replace what was broken.
I cannot stress how much easier it is to remove exhaust hardware if you let it soak overnight with WD 40 or even better, PB Blaster. Use a liberal amount on each nut and bolt and wipe it off too remove excess rust in between soakings. It makes life a lot easier and can literraly get hardware off easily that would have stripped or broken without using it.

Do one of the nipples attach to a vacuum pot?

If you get a chance, take a look at rockauto. Com. I realize that this is just a difference in the finish and shape. The one I found is wrinkle black finich and has two nipples on it. One on the vacuum pot and one on the other end just going into the pipe.
See if that looks like what you need to fix. If it is not it is probably an air injection pipe and you will have to get that from a dealership or a salvage yard.
Is the part cracked?

Did you find the part at the site I mentioned?
It looks more like what you described, they have a great catalog with pics of the particular part by the manufacturer and all in a zoom view, I thought it might help to see it and figure out if it was what you are looking for.
Let me know.

Then I looked under Lexus, 1995, ES 300, then click the Emission tab and then the EGR Valve tab and there are two to choose from. The Airtek one is the black wrinkle finish and was more of what you described. So, I thought it would be worth you taking a look at.