I just read an article in a magazine called like auto world that used the "Tornado" thingy that does what the products already stated do. Well, they tested it on a '99 Chevy Suburban with a 7.4L and it added .1 sec to the 1/4 mile time and like .5 mph. It also reduced gas mileage by 1 full mile per gallon. It probably poses more of a restriction than anything else and at like $80 it's a total rip off. Swirl is already built and tuned inside the induction system of a car (ever heard of "tumble port" heads, or "shrouded valves".) If anything this product may help a LITTLE bit on the lowend, but it has to restrict flow somewhat. Just my opinion.
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'84 Mustang 5.0 LX
My car