ok, throttle body is in:
i used the oem rubber boots to install the plenum (otherwise use two 3.75" to 3.25" reducers). you can see the aos tube; not connected but will go on once i get some heat on it. the whole thing clears the engine cover, throttle connector plugs right in. removed the bracket that the previous throttle body bolted to; replaced the bolts that held it in place because they went straight through to the bellhousing (used washers to get same depth as previous).
so, final parts list is:
one $42.43 997 110 416 03 997 plenum
two $ 3.05 999 512 539 01 hose clamp (for the larger plenum)
four $ 0.27 900 385 025 04 bolt (larger throttle body requires shorter bolts)
four $ 0.15 N 011 524 27 washer (for above)
one $ 5.49 997 110 319 00 throttle body gasket
and one 74 mm throttle body from a 996, 987 or cayman. i bought mine used for $100 as there are lots around (996 from wreckers, cayman from guys who do the gt3 throttle body mod to their cars); find the right seller and you should be able to get the bolts, washers and gasket as well.
the final step is the connection from throttle body to maf housing. you need a 3" duct that will mate to the 3.25" flanges on the throttle body and the maf housing. i recommend the following $20 spectre 3" flexible duct because it has a rubber lip that should stretch to 3.25":
3" Dia Air Intake Flexi Ducting Air Intake Tubing Expands for Universal + CLAMPS | eBay
i haven't done that as i'm doing a custom intake as part of this project, but figure it should work ok. other options are a custom silicone build or repurpose the oem duct in some manner. regardless, all in for under $200.
and no, i've no idea if it improves power; by the time i get my car running i'll have the larger plenum and throttle body, new intake, udp, deleted AC, cleaned injectors and lighter rims; i'll have no idea where the improved performance is coming from (as long as there is improved performance ...).