I think the
writers at Hot Rod (and Frank McGurk) would disagree with Hot Rod. Just adding headers to a 261 increased horsepower by almost 4 percent, and adding a dual intake manifold with two 1 bbls added 16% more horsepower. The combination of the two should yield (based on these tests) about a 20% increase in horsepower.
I never had my truck tested, but it certainly didn't hurt performance.
