Very important information to understand when looking at dyno results:

Dyno-testing on any car can has many variables that affect measured results.  One critical factor that makes accurate and repeatable dyno results is the OBD-II (On-Board Diagnostics, 2nd generation) that by federal requirement is a part of all 1996 and newer vehicles' engine management system (US cars only).  The OBD-II equipped DME engine management system has a variety of adaptive features that monitor vehicle use and will actually change the maximum of power the engine can put out, all without any actual mechanical changes having been made.  Interestingly enough, the simple act of applying full-throttle application in a dyno run will cause the adaptive DME to increase available power.  It is not unusual to make three consecutive dyno runs and see the power output increase with each run, with no changes made to the vehicle.

Even more importantly, it is important to understand that no two cars are identical.  Minor variations in engine parts manufacturing, assembly, and initial break-in periods can cause two otherwise identical cars, even built consecutively on the assembly line, to have power output variation by as much as 5% or more.  Effectively, comparative dyno results for the purposes of evaluating any performance product have an inherent inaccuracy if two different cars were used.  The only way to get truly accurate comparative numbers between two different products is to test the exact same car, at the exact same time, on the exact same dynamometer.  Along the same lines, two different cars may react differently to the exact same performance modification, one showing higher results than another.

With all of the above information in mind, dyno results from installing the UUC Underdrive Pulley Set can vary from a minimum of 4hp to a maximum tested 11hp.  This is an "average" dyno graph showing relatively consistent change throughout the rpm range:

(click picture for a larger view)