Intake Ducts Removal
You will need to remove the intake ducts in order to remove the throttle bodies assembly or to install aftermarket ducts.
Do First:
Remove the Bulkhead Doors (see Bulkhead Covers Removal, steps 1-2) .
Tools:
4mm hex tool bit
silicone lubricant
clean rag
small sheets of plastic
rubber bands
torque wrench
1. Use a 4mm hex tool to loosen the duct clamp bolt (circled in pic below) on each of the two throttle bodies located at the left engine bank.
Open both clamps but do not try to remove them. Free the clamps if they are stuck to the duct. Be careful not to bend the clamps, they are made of a soft, metal.
Removal
2. Apply a film of silicone lubricant around the outside of the duct.
Press up on the bottom edge of the outer duct while pulling up inside the top of the duct from inside the air box. The clamp will drop right off of the duct onto the bore of the throttle body.
Remove the clamp and the duct. Wash off with silicone lubricant and a clean rag.
Remove the inner duct in the same way.
Replace the bulkhead door with bolts finger tight to prevent contamination by foreign material.
3. Cover each open throttle body bore with a small sheet of plastic and secure it with
a rubber band so that no foreign matter can fall in. 
4. Pull the grommet out of the duct holes in the air box. Clean the grommet with silicone lube. 
5. Apply a film of silicone lube around the edges of each hole.
Lay a sheet of plastic over the holes and reinstall the grommet so that the air box will be sealed from any small debris that may enter.
Place the bulkhead door back on and tighten the bolts finger tight. 
6. Follow the same procedures in steps 1 through 5 to remove the ducts from the RH throttle body bores.
Installation
7. Remove the plastic covers from the top of each throttle body bore (step 3).
Place the duct clamps over the tops of the throttle body bores with the clamp bolts situated as shown in the diagram and photo below. The clamps are made of soft metal. It is not necessary to stress the metal by bending it.
8. Remove bulkhead doors.
Remove plastic dust covers from grommets (step 5).
9. Install ducts #2 and #3 first, then install the outer two ducts.
Apply a film of silicone spray lube to the outside neck [C] of the ducts and the inside of the grommet [A]. Also to the top outside edge of the throttle bodies bores. 
Push the ducts through the grommet in the bottom of the air box. Make sure that the pin on the Duct [D] aligns with the hole in the clamp [E]. 
10. Lift the clamp onto the bottom of the duct engaging the pins on both sides of the duct to the holes in the clamp.
Torque the 4 clamp bolts to 18 in lbs using a 4mm hex key bit.
11. Install bulkhead doors (see step 4, 5 and 6, Bulkhead Doors Removal).