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It probably doesn't work as well as an actual exhaust brake
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I'd have to say that I don't see how "an actual exhaust brake" could work any better than the EBPV type brake I've been using for almost 6 years actually works. Course mine is on a manual shifting truck and maybe they work better on manuals than automatics??? I do remember before getting mine, driving in someone's automatic truck with the brake and it didn't slow it down as much as mine does on the manual. I do think these things (the EBPV type and not the actual exhaust brake type) are well worth having on your truck though.