Independent tests have shown average gains to be in the neighbourhood of +15-18 horsepower with the occasional +20-22 hp on really efficient combos! Drop-In cams are indeed drop-in but proper installation (checking all critical clearances and degreeing) and tuning are still necessary and many times may be the difference in the numbers you will see.
These Camshafts are "Drop-In" type camshafts - This only means that they do NOT require the use of aftermarket valvetrain components. A professional tune is highly recommended to ensure proper idle, air/fuel ratio, and peak performance. Proper installation is still necessary to achieve optimal performance gains. Pro XP Valve springs (P/N 311-05-7380) + Titanium Retainers (P/N 308-05-0410) are recommended when using these camshafts in Forced Induction Application. Lobe Centerline: Intake: variable (adjust with ECU).