Go to the Accufab site and read some of the articles and numbers on their tests of throttle body/plenum combos. Fact of the matter is, you should really do the intake shuffle.......new plenum, throttle body and CAI all at the same time to get the most out of your new system. They are all meant to work together. One without the other just will not do your Mustang justice. The only real guideline I would suggest on CAI's is go with a fender mounted air filter model. That is where the hi-flow air cleaner is actually put through the air silencer hole and into the fender well so it does not suck in hot air from the engine compartment. Cold air is always denser. BBK is this configuration and so is Densecharger. I am sure some others are similar as well. Pros and cons on metal intake tubing versus cool plastic also. The metal intake tubing such as BBK looks much cooler under the hood but will actually heat up under heavy use. I think the air flow really is not effected as some may think as it really travels way too fast to manage to heat itself beyond a normal level.