The tb spacers really don't do much as far as power in concerned. I used to have a bookmark for an email thread directly from air raid stating basically just that. The twist, helix, twirl whatever the maker wants to dub them do however help a little as far as mpg is concerned. During wot the air is moving too fast for a tb spacer to really effect the incoming air. During regular cruising where the air is moving slow enough to be effected it creates a better fuel mix thereby also creating a few extra numbers. Don't believe Thier sale tactics that it increases hp I mean who gives a crap about more power when your cruise control is set. However if your trying to gain a little extra mpg (driving a billboard on wheels who doesnt) give one a try. I suggest transdapt brand if they make one for your truck. Thier prices are way cheaper than the big brands and they do the same thing.
