These kits offer higher levels of rotor sound (whine) within the cabin due to the direct path from the inlet through the firewall and the larger ID.
Image Above : Stage 4 Kit
Image Above : Stage 5 Kit
These kits DO NOT require that the firewall is drilled.
Stage 4 kits have a 1-1/4” OR 32mm step drill bit
Stage 5 kits have a 1-5/8″ hole saw drill bit
1 x diaphragm cap
(Stage 4 sound tube kits have a 1” 90° inlet elbow)
(Stage 5 sound tube kits have a 1-1/4” 90° inlet elbow)
2 x rubber grommets 1 larger (firewall grommet) 1 medium (inlet grommet)
Disconnect your boost hose from the boost gauge supply line fitting inside the truck. This fitting is located under the dash to the right of the steering shaft assembly (The boost hose and grommet are located a little up and to the right of the steering shaft assembly like shown in image - right).
NOTE: I have pointed out the steering shaft under the dash with a BLUE oval for an easy reference point (its really dark under these dashes without proper lighting and hard to see).
Locate this steering shaft and the boost hose and grommet pass through the firewall where I have drawn the RED circle, slightly up and to the right of the steering shaft. Grab the boost hose and follow it up to where it plugs into the boost fitting. Once located, disconnect the boost hose from the fitting.
Once the boost hose has been disconnected from the plastic boost fitting, push outward on the firewall grommet from inside the cab. The grommet should push out of the firewall fairly easy with any decent amount of outward pressure and it will fall into the engine bay and be resting for you on the other side of the firewall like pictured.
Now just disconnect the boost line on the engine bay side like in image and remove the boost hose and grommet assembly from the engine bay.
You should now have the boost hose and grommet out of the engine bay like pictured below in image, right
Now firmly grab the rubber elbow and twist it back and forth while pulling it away from the hose and it will come off like pictured below in PICTURE
Now that we have the boost hose out of the truck, locate the boost gauge side of the hose with the 90° rubber elbow like in image , left
Set this rubber elbow to the side and keep track of it, we will be re-using it.
Next we are going to slide the OEM firewall grommet off of the boost hose.
NOTE PICUTRE – below: This grommet is on the boost hose pretty tight so I suggest finding some kind of lubricant and putting a light coating on the boost hose so that the grommet can slide off of the hose easier. I used soapy water and it came off pretty easy
Slide the grommet off the boost hose and then re-insert the 90° rubber elbow we removed earlier like in PICTURE below.
Step 1 is now complete, once the 90° elbow has been reinstalled set this hose aside along with the firewall grommet and prepare for step 2!
Remove the 3 vacuum hoses on the bottom of the intake tube, they pull straight off the barb's they are connected to. Next disconnect the Intake Air Temperature Sensor connector. Next disconnect the intake tube from the throttle body (8mm socket or flat blade screwdriver needed for hose clamp) and Mass air flow housing (8mm socket or flat blade screwdriver needed for hose clamp). Once both ends of the intake tube are loose remove it from the engine bay.
Stage 2 Kits With supplied step drill bit tape off the last tier of the drill bit so when your drilling the hole you know when to stop drilling (drill to second to last step 1 ¼’ or 32mm) like in PICTURE – 2C BELOW...(DO NOT DRILL TOO FAST AND DRILL TOO FAR INTO THE INTAKE TUBE OR YOUR KIT WILL NOT SEAL CORRECTLY).After you've drilled the 1 ¼” or 32mm hole, insert the rubber grommet provided in the kit like in PICTURE below.
Stage 3 Kits need to grab the 1-5/8” hole saw drill bit that was supplied in your kit and drill in the same location shown for Stage 2 kits (right in the middle of the casting mark like in PICTURE.
After you've drilled the hole, insert the rubber grommet provided in the kit like in PICTURE.
Install the sound tube by carefully pushing the 90° elbow through the rubber grommet in the intake tube like pictured below in PICTURE - 3A and 3B.
This variation is normal.
Next start feeding the intake tube back into position while routing the sound tube under the throttle cable bracket and brake booster vacuum hose like in PICTURE right.
As you start to put the intake tube back into place you'll need to work at both ends ensuring the sound tube goes through the firewall grommet next to the boost hose like in PICTURE right.
The intake tube needs to be put back onto the MAF housing and throttle body but NOT TIGHTENED down yet, leave it loose. Go ahead and re-install the 3 vacuum lines on the bottom of the intake tube and connect the intake air temperature sensor connector on the back side (hearing it click tight) then install the 10mm bolt for the support bracket on the bottom and finally tighten up the 2 – 8mm hose clamp bolts at the throttle body and MAF housing... It should now look like a truck again like in PICTURE.
Have someone hold the sound tube firmly on the engine bay side of the firewall and then push the diaphragm cap on securely to the end of the sound tube like in PICTURE
Lastly plug the boost hose back into the boost fitting inside the cab under the dash and check over all your work one last time before starting the engine of the vehicle.