It seems to be a very popular question around here and many other 4.6L Stang forums,"What kind of Throttle Body and Intake Plenum is the best, and is the ACCUFAB really worth it?" Before I bought mine I did a lot of research. I found out a lot. The links below tell you everything you need to know. I have posted about this topic in several different threads in the past few days. I hope this helps you make you decision:
http://www.cnlperformance.com/plenum.html
http://www.modulardepot.com/?show=articlesdet&aid=38
So after looking at these sites, some conclusions to be made. Yes, the Accufab Plenum is the best, but recall the dyno numbers.
These are some numbers for the independent dyno runs you guys saw in the link: (Note all Plenums listed are using the Accufab 75mm TB)
Stock
RWHP 265.97
RWTQ 303.54
Accufab
RWHP 272.38 (+6.31)
RWTQ 310.42 (+6.88)
C&L
RWHP 271.13 (+5.16)
RWTQ 306.05 (+2.51)
Dragon
RWHP 270.69 (+4.72)
RWTQ 307.27 (+3.73)
Trick Flow
RWHP 270.19 (+4.22)
RWTQ 306.61 (+3.07)
So we can see it really doesn't make that much of a difference. But, how much do you want to spend? That should really be the deciding factor. The Accufab combo is the best, but it also runs about $400, the rest are about $300, depending on where you look, many sites offer the Accufab TB with the other plenums. Is the extra $100 really worth it to you, that's what you have to decide. It is not necessarily the HP you are getting fromt his upgarde anyway. It is the improved throllt response. And not only does it help with a great improvement in throttle response, it also helps smooth out your powerband.
Now when it comes to deciding what throttle body size to get, a lot of people around here will tell you that a N/A (naturally aspirated) car does not need a 75mm TB, and to just go with the 70mm. I disagree. The reason I posted the first hyperlink was to show everybody that the 75mm TB does make a difference in horsepower from the 70mm TB. Take for example the first test between the BBK 75mm TB and the Ford Racing 70mm TB, and the Accufab TB's with the Ford Racing TB (note: all tests with C&L Plenum)
Test 1, on a slightly modified Stang
FR 70mm
RWHP 267.99
RWTQ 308.28
BBK 75mm
RWHP 270.27 (+2.28)
RWTQ 312.65 (+4.37)
Test 2, on a different Mustang
Ford 70mm
RWHP 251.60
RWTQ 291.74
Accufab 70mm
RWHP 253.17 (+1.57)
RWTQ 294.50 (+2.76)
Accufab 75mm
RWHP 261.64 (+10.04)
RWTQ 304.32 (+12.58)
All the dyno charts can be found in the first link. The difference between the Accufab 75mm TB and the 70mm TB is
+8.47 HP and +9.82 TQ. Why wouldn't you want the 75mm TB over the 70mm TB if they are the same price. With the Accufab combo they give you the choice of the 75 or 70mm TB with your purchase. Anyway, IMO you should get the most HP for your dollar, so if someone if willing to offer you a 70 or 75mm TB go with the 75mm. It shows at least a few HP gain every time. Even though everyone says you don't need it, it will not hurt you in any way, only help you get more HP. Isn't that why most of you are here, more HP for you $$$$$$$$. I am sure someone is going to disagree with me and say you don't need the 75mm unless you have a S/C or turbo, but before you do, just check out the numbers. More HP for the same price, do you really need to think twice about it?