Your sig says nothing about a 4.6 car so I am just going to assume that a 4.6 is what you have. Don't bother porting the plenum, you will get much better (although still meager) results going with an aftermarket plenum. As for porting your TB, you shouldn't do it for at least 4 reasons.
1. You need the air moving through the TB in very particular way. TB's are designed so that the change in throttle body position results in a smooth change in air allowed to pass the blade. Porting will change the way the air flows through the TB and you ruin this linearity. It won't be as extreme as zero to WOT with a fraction of an inch pedal movement, but it certainly won't be nice and consistent either.
2. If you port the area right at the blade, you will allow more air to pass the blade when it is closed. That will royally jack with your idle and probably cause you to burn a LOT more fuel when not moving. If you port everything except the blade, its still going to have the same airflow as before because the diameter at the blade's location didn't change. A royal waste of time.
3. At stock levels the TB is absolutely not a restriction. You will gain nothing even if you bought a new larger TB. Spend your time and money working on the components that will actually provide results. To give you some perspective, the stock TB for the 5.0 (302 CID) was 55mm, the stock TB for the 4.6 (281 CID) is either 65 or 70mm (can't remember which).
4. If more flow out of a TB is something you absolutely just have to get, I am sure there are a LOT of people around here that would gladly sell you theirs for a lot less than retail to recoup some of their loss.
Not trying to bash you, just trying to prevent you from wasting your time and money.