You said the intake air duct is a large ribbed hard plastic hose but what is it attached too. i only found a soft ribbed hose

Large ribbed hard plastic hose, black in color

Hard to believe you have a bad MAF in a 2007 caddy. How many miles on car? Have you tried cleaning the unit?

Parts store have a locator chart which should show location.

It is looking at you, when you open the hood

You go from the air cleaner box thru the plastic
ducting hose to the intake manifold

The engine air intake filter is located next to the driver's side end of the engine in a large black plastic housing. Housing is diagonally between the windshield washing fluid resevoir and the radiator. You have to remove two screws from the top of the housing and remove the electrical connector from the large flex air hose at the back of the housing. The air hose fits tightly into a groove around the air intake on the engine and needs to be pulled back and off. Then the housing rear section and the attached air hose can be moved back and up out of the way.

1. Standing in front of the vehicle it's on the left front side of engine kind of low.
2. Be sure to get a gasket as well.
3. Drain the cooling system.
4. Loosen the air cleaner outlet duct clamps at the following locations:
   • Throttle body
   • Mass airflow/intake air temperature (MAF/IAT) sensor
5. Remove the radiator inlet hose clip from the outlet duct.
6. Remove the air cleaner outlet duct.
7. Reposition the outlet hose clamp at the water pump.
8. Remove the outlet hose from the water pump.
9. Remove the water pump inlet bolts.
10. Remove the water pump inlet and thermostat from the water pump. Water pump inlet/thermostat assembly location

To install:

1. Install the thermostat and water pump inlet to the water pump.
2. Install the water pump inlet bolts.
3. Tighten the water pump inlet bolts to 11 ft. lbs. (15 Nm).
4. Install the outlet hose to the water pump.
5. Position the outlet hose clamp at the water pump. NOTE
   Important: Align the arrow at the throttle body end of the duct with the throttle body attaching stud.
6. Install the air cleaner outlet duct.
7. Install the radiator inlet hose clip to the outlet duct.
8. Tighten the air cleaner outlet duct clamps at the following locations:
   • Throttle body
   • Mass airflow/intake air temperature (MAF/IAT) sensor
9. Tighten the air cleaner outlet duct clamp screws to 62 inch lbs. (7 Nm).
10. Fill the cooling system and check for leaks.

Read more: http://wiki.answers.com/Q/Where_is_the_thermostat_located_on_a_2001_chevy_suburban#ixzz1TvIO3kpD

The Intake Air Temperature (IAT) sensor is the same as the Manifold Air Temperature (MAT) sensor on earlier models. IAT is located in or near the air intake duct (click image for zoom).



Fig.: On 1996-98 vehicles, the IAT sensor is mounted in the rear air intake duct


Hope this helps (remember to rate this free answer).

LOOK UNDER HOOD TO THE RIGHT ON DRIVER SIDE.YOU SEEN A BLACK PLASTIC BOX WITH A AIRDUCT WITH LARGE CLAMPS AROUND AIRDUCT GOING TO MASS AIR FLOW TO THROTTLE BODY.THE AIR FILTER IS INSIDE THE BLACK PLASTIC BOX.TO REMOVE AIR FILTER.FIRST YOU DISCONNECT MASS AIR FLOW SENSOR ELECTRICAL CONNECTOR..LOOSEN THE HOSE CLAMPS THAT SECURES THE AIR INTAKE DUCT TO THE THROTTLE BODY THEN LOOSEN REMOVE THE FASTNERS ON AIR FILTER COVER THEN LIFT REMOVE COVER AND REPLACE AIR FILTER THEN PUT EVERYTHING BACK VISA VERSA.

You have a vacuum leak, possibly from a small hose or the rubber intake hose to the throttle body that is large, and ribbed. You may have a tare inbetween one of the ribs or other area.

Follow the large radiator inlet hose from the radiator, to the thermostat housing. Once the housing is located, simply remove the housing to expose the thermostat. It may be necessary to remove the air cleaner and duct assembly, and the crossover exhaust pipe, as well.

I assume it is a turbo diesel? Then:

Location of the sensor:
- in early cars is in the ECU, with vacuum pipe going from intake maniforld duct to the ECU
- later models on the air intake duct, with wiring going to the ECU.

The fault may often be caused by:

- air leaks in MAP sensor line to the ECU (early ones only) or any of the vacuum control line hoses. This normally due to perished/loose flexi pipes, etc).
- leaks in the air hoses going between turbo/engine/intercooler. Can be spotted by slight oil contamination at the point of leak.

Or it's variable vaine sticking (even intermittently) in the turbo due to contamination, preventing the turbo from performing according to the ECU demand, and hence being 'shut-off' by th ECU

So - check all vacum line for leaks, ensure turbo actuator is free to move, all air hoses are intact and secure, intercooler not leaking.