Pictured here is the "start line", where it all begins after clean-up.

This pic was extremely difficult to get clean and crisp as the camera kept focusing on the back of the internal plenum thru the TB flange. Then when I put the rag in and centered the gasket the shiney gasket surface ket washing out the I.D. edge of the gasket so I outlined it in black. I also test-fitted 15-20 TB gaskets to make sure the first one wasn't a fluke. All showed the same HUGE 6 o'clock-to-12 o'clock gap. This is a SERIOUSLY large impediment to flow when your thorttle body secondary butterfly opens as well as when your manifold switchover occurs. Big as it is and with the other work we'll be doing here this area alone "could" yield an at or near 5-7HP improvement at 4.5k+ RPMs and up. That gap is nigh on 1/8" thick(.118") at the 9:30 position. By flow standards and velocity at that spot it is HUGE HUGE HUGE! Plus it's deflecting GOBS of air to the opposite side of the intake making the left bank have to work harder for equal air.... it's a restriction, an imbalance and a huge turbulence creator in an area that craves smooth air. And it can't just be cut at an angle just below the gasket... it has to be bored on a smooth, gradual taper all the way to the outlet, over 3/4" deep! It is a surprisingly large mis-match by Audi standards.

Before I tightened the bolts down to hold the gasket in place while I took the photo I did it "just" as you would mount one on the car, ie; in the horizontal position and let gravity nestle it downwards just as if you were replacing one on the car. Does no one any good to install it differently than "real-world" situation... centered for the project then horizontal in real life.

This flange I.D. needs to opened up dramatically to match it to the gasket on the bottom left-to-top right corner. Surprisingly the gasket is a very good fit as-is to the throttle body base.

Also we'll be removing, then filling the nipple in the top of the flange for even better flow. That nipple is actually a threaded sleeve that is used by one of the bolts that hold the upper/lower manifold shell halves together. We'll be grinding it flat, sealing it with epoxy putty then smoothing/sanding and light-polishing it along with this entire inlet area. Then we'll have to source a shorter bolt for that particular location.

If this doesn't send you Dremel owners to the store for some larger HP equipment you'll skate fine thru the rest of the project.