Not surprisingly, enhanced breathing brought about by the HCI extended our test-Pony's rev window, allowing it to make impressive power from 4,900 to 6,900 rpm. It's hard to pinpoint exactly which piece is the key to the overall gains, as the entry-level pieces and intake manifold showed us only modest increases in rear-wheel horsepower and an across-the-board decline in rear-wheel torque within the 2,600- to 6,100-rpm parameters. But this doesn't mean the bolt-ons aren't effective and shouldn't be considered. To the contrary, we think the larger throttle body and CAI (and sharp tuning) are essential pieces for the overall HCI upgrade.
This HCI top-half mod from AMP Performance is a safe bet for enthusiasts who want to make steam naturally, and we're confident it will really show off for those who wish to add forced induction to their '05-'10 'Stangs.