I agree w/ high intensity cardio. However, I do intersperse the workouts w/ regualr low intensity workouts. Generally I do 2 and 2. I find this helps get leaner, preserve muscle, and it does not effect my strength.
Monstar
One other thing, if i where you, i would begin timing my rest intervals. If you keep those constant, you will have a better understnding of when to increase your cardio.