I've used (and will ONLY use) Eastwood's aerosol Aluma-Blast on the throttle body. 3 coats, then a clearcoat of your choice from Wal-Mart, and it's show-quality.
I also use Eastwood's Aluma-Blast on all of the other aluminum underhood pieces. Intake, plenum, accessory bracket, etc.
More expensive, but second to none. Good luck.