Well, TB size really isn't a safety issue, it's more a matter of how much air you can actually suck in, before you overwhelm your car, and it takes too long to fill the plenum. Most all motor cars with a couple of exceptions run between a 64-68mm, some being flared from a 70mm down to what ever size they were running previous. You really don't need anything larger than a 68mm unless you're really pushing some huge cams(Toda Spec-D), and lots of compression(16:1), and even then 68mm is really big.

As far as injectors go, you really should decide your size based on your mods, rather than basing your mods on your injector size, you'll get a lot further that way.

In any case, good luck,
Aj