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Breath-ability is your car's performance best friend.  When you start to modify your Mustang, you want to be able to get as much air in, and allow it to escape just as easily.  Installing a high performance straight shot filter and intake tube is the best place to start followed by a freer breathing exhaust.  An X-pipe/Catback combination really rounds out the mods from front to back.

With these enhancements in place, there is one thing left to do that will significantly improve the performance of the 4.6L GT motor.  A larger Intake Plenum Chamber and a larger throttle body.   This article will deal with the installation of both including a spacer plate with some porting instructions thrown in for good measure.  The spacer plate servers to produce better torque figures in the mid-RPM range as the engine is spooling up.  This is not a necessary part of this installation and does not have to be added.

The stock intake chamber for the 4.6L is really an inefficient design with how sharp a 90 degree corner the air takes before entering the intake manifold.  There are several options on the market for the 4.6L and most of them are very close on the hp improvements they provide.  You choice will come down to your price consideration and looks.  Some of these choices are painted, some are a satin finish right up to polished and chromed items.

We have been fortunate to work with MAC Performance and will be installing a polished Intake Chamber and a MAC 75mm throttle body.  

We also purchased a 1/2 spacer plate, but this will require several hours of grinding with a Dremel tool to port the Intake to the plate properly.

Let start by demonstrating the stock arrangement and indicating what the various components are that you will be dealing with.

To begin, we won't remove anything until we have ported the opening properly to match.  Air is affected by several factors such as Parasitic Drag and turbulent flow.  There is not much you can do about Parasitic Drag except scrap the stock rubber intake tube for a high flow intake.  Turbulent flow however, can be minimized by removing all the areas where airflow gets disturbed.  When you mate the throttle body to the intake chamber or the intake chamber to the plate, feel with your finger if there is any lips that the air had to travel over on it's way to the engine.  Those are the areas that we will remove as much as possible to minimize disturbing the flow of air.  The best way to really know how much you will remove is to trace around the openings of the intake chamber and the spacer plate with a market pen.  Put the two together as they would be assembled and scribe with enough pressure to make a mark.

Both sides of the spacer needs to be ported but we won't be able to mark the engine side until the stock intake chamber is removed.  When you are grinding material off with the Dremel, tilt the Dremel at an angle so that you are only remove material to about the 1/2 point thickness area.  Then we we can scribe the other side, we can turn the plate over and match up the two sides of the plate.

Now that we have completed all the porting that is required, we are going to start removing the stock intake to make room for the new install.  Start by loosening the intake tube clamp at the MAF as well as the one right at the stock throttle body.  There should be enough movement and room to back it off, out of the tube adapter the mates it to the throttle body.

On the drivers side of the intake is the EGR valve assembly  (refer to the first photo for identification).  Loosen off the pipe fitting and remove the tube from the EGR valve.  There are 2 bolts that mount the EGR to the intake.  Remove this and carefully remove the EGR valve.  If the graphite gasket is partially stuck to the intake and the rest came with the EGR valve, you will need to get a new one from your local Ford dealer.  Cost me about $2.30.  After the EGR is removed, go to the opposite side and remove the 4 bolts that hold the throttle body to the intake chamber.

Before remove the 5 mounting bolts that secure the intake chamber to the intake manifold, we need to free up the throttle/cruise control linkage.  There are 2 bolts that secure a bracket to the top of the intake chamber.  Remove the spring return from the bracket first, then loosen the bolts.  The cruise control linkage is the plastic lined connection, it will just snap off of the connector point on the throttle body.   Grasp the throttle body and open the throttle, this will allow you to get some slack in the throttle cable and remove it from it's mount.

It is now time to remove the vacuum line, electrical connection for the throtlle positioning sensor and the AIC motor from the intake chamber.  mounting bolts for the intake chamber.  The vacuum hose may require a little persuasion with a screw driver or pry tool.  Be careful when removing the AIC motor to prevent damage to the gasket.  You will need to re-use this gasket on the new intake chamber.

With all the extremities free, we can remove the 5 bolts holding the intake chamber.

Careful lift up on the stock chamber, there is a rubber ring gasket that seals it to the intake manifold.  Once it is free, it will allow you to remove the emission hose on the back side of the chamber.

We found it easier to mate the 75mm throttle body to the new chamber first utilizing the supplied gasket as well as the adaptor for the 2001/2002 PCV valve.

Carefully position the newly assembled intake chamber over the intake manifold and start threading the 4 mounting bolts, leaving them loose.  Since we have added an adaptor plate, there is a small spacer that is supplied to put under the support leg of the intake chamber.  Carefully tighten in a opposing pattern, the mounting bolts.  DO NOT OVER TIGHTEN THESE BOLTS.  They are mounted in a plastic intake manifold, over torque these bolts and you could crack or strip out the threaded inserts.

Reassemble the AIC motor, the EGR Valve with a new gasket and tighten the pipe fitting securing the pipe.  Reconnect the vacuum feed and transfer the throttle positioning sensor (TPS) from the old throttle body onto the new throttle body and reconnect the wiring harness to the TPS and  AIC motor.  Don't forget the Evaporative Emission Return hose on the back side of the chamber.  Reconnect the throttle/cruise control linkage and spring return.  Check to see that there is full motion and operation of this linkage with not interference.   Re-install the intake tube and tighten the hose clamps should complete your installation.  Check for any tools, stock part or fasteners lying around the engine compartment before closing the hood.

Start the engine and check for any vacuum leaks.  Let it idle for a few minutes until the engine actually warms up.  This will allow the computer to learn a few things about the new mixtures that is needs to compensate for.  Take it for a short drive, driving normally without pushing any limits.  After a few miles, give it a test and feel the new response and torque you will feel.  This is another good Seat of the Pants install.  Enjoy.