It is the one that goes under the intake manifold to the front of the car at the thermostat housing. I see the thermostat housing looks to be bolted down via two bolts. I was able to use a 3/8 extension (a long extension) and remove 1 of the 2 bolts from the water pipe flange via the rear of the engine after having removed the EGR. The other bolt on the driver side is squeezed in pretty good. I may go buy an extension that is 1/4" and see if it can wiggle in there.
Follow Ups
How do you remove center heater return pipe? - evan_aggie10:08:37 04/08/11