Well I didn't do all the work myself so I can't give you all the details! But it went something like this:
* Design, and get machinst friend to make, a flange for the throttle body. We made it out of 3/8" aluminum, and I bought a TB gasket to use as a template. Basically he made it in rectangular shape, then I used a hacksaw and file to cut the outside down to exactly the right shape. This is mostly so the welder could easily get access behind it, otherwise having a little extra hanging off the sides is not a problem.
* Find a piece of pipe to go between said flange and the manifold. Aluminum of course. A place called onlinemetals.com has aluminum "strutural tube" which is 3" OD and 2.625" ID which is just about the ideal size. Usually it's sold by the foot, but they have 10"-12" "leftovers" they sell for semi-cheap (I think I paid ~$15.00).
* Cut the end of the tube at about a 30-degree angle to mate up with the manifold. The end that mates with the TB flange is straight.
* Have your friendly local welding+fab person modify the manifold by removing the old TB mounting (cut off with a bandsaw), cover the hole left behind by removing it (fabricate an aluminum plate and weld it in place), and enlarge the front area upward to accept the above-mentioned tube. The enlargement is due to the fact that to clear the PS pump (this is with the standard AAN serpentine-belt setup and an A6 pump) the TB must be mounted up fairly high. This photo shows the manifold as modified in this step:
And this shows me holding the tube up for a test-fit. You'll notice there was a "nub" left over on the casting where the TB mounting used to be that interferes with the tube. I took it back to my guy and he ground that entire area down flat which made things much easier:
There are also some holes, or more properly tubes, going through the manifold to make it easier to gain access to the bolts holding the manifold to the engine. Some of those will have to be removed and the resulting holes plugged. One of those tubes was where the "nub" is in the photos above.
* Attach the manifold to the engine, also of course have the PS pump in place (or anything else that might pose a clearance problem). Attach the TB to the flange. Figure out what position you want the TB to be in - the purpose of this exercise is just to figure out how long the tube should be.
* Cut the tube to the length you determined in the last step.
* Using two of your hands, hold the TB+flange+tube up against the manifold and decide what position you want it in, paying attention to clearing the PS pump. Using your third hand, mark the tube's position on the manifold and TB flange.
* Take the manifold off the engine. Using a pen, mark the contour of the inside of the tube where it meets the manifold.
* Use at least 17 tools, including at least 4 you don't own, to make a hole in the manifold that matches the inside of the tube. Since the tube is angled, the hole is oblong so don't think you're just gonna get away with using a hole saw! Seriously, I used a drill to make a series of holes around the perimeter, a saber saw to cut between the holes, then a Dremel tool and file to finish/smooth it off.
* Take the TB flange, tube, and manifold back to the welding person and have them weld it all together.
* Enjoy!
By the way, you may have noticed there's no throttle cable there. That's going to have to wait until I get the engine into the car and I can see how that needs to fit together.
