Cat's ACERT technology is after 2008, so if you want to model a C15 in an older model truck, or if like me you just want to have a model of an engine that in the real world actually WORKS, then here is how to change the turbo set up on the C15 to look like the pre ACERT turbo.
Step One
Remove the turbo unit from the engine. Be careful and make sure you get both of the turbo oil return tubes. There is one from the center of both turbos going to the block.
After you get the turbos off refer to picture #1
Cut the top turbo exhaust pipe just below the flex tube. (Red & Green Arrow)
Discard the box that is behind the bottom turbo between it and the block. There will be a hole where that box is mounted that you will have to cover.
Step Two
Refer to picture #2
Cut the intake to intake pipe between turbos where the pipe goes into the top turbo. (Red & Green Arrow)
Your two turbos should now be separated. Discard the bottom turbo, the top turbos is the only one you will need.
Step Three
Refer to picture #3
Discard the parts shown with a RED arrow, they will not be used.
The air box that is marked by the Blue & Green arrows will not be used and can be, or should be, removed. However again there is a hole in the block to mount this box and that will have to be covered.
Cut the intake out tube coming from the turbo at the point where the RED & GREEN arrow is pointing. You may choose to do this after completing step #4.
Step Four
Refer to picture #4
Cut the turbo sections apart between the intake side and the bearing oiler.
(RED Arrows)
Turn the intake so that the exit tube is up and out at about a 30° to 45° angle facing up. (Blue & Green Arrow)
Now just glue the turbo parts back together and install. that's it.
-Mike