What are they and what do they do? Who makes the best ones also? I know bigtruck311 has one on his truck.

 

no i dont, they are a a wast of money, they are sapposed to spin the oncoming air charge and give you better atomization of the air fuel mix, now on old throttle body or carbed applications they work, on modern multi port fuel injected vehicles they do nothing but empede air flow vilecity, it will make you lose HP not gain, i repeat they are worthless do not get it, do a search on the subject and you will get a longer explanation, good luck