Two common causes of itching are also mites and stud tail/feline acne.
Mites - these are usually around the face and neck, and perhaps the upper part of the body if the case is bad. The revolution should have killed any mites if this was the problem though. This is terribly itchy.
Stud tail - Some cats produce a lot of grease/oils on their skin in response to hormones. The oils are hard for the cat to clean off, and can build up leaving yellow dandruff, and scaly, itchy skin. This is generally worse on the base of the tail and lower back, and can also be seen as "acne" spots on the chin. Washing off the troubled areas with shampoo helps especially if the cat can't reach. After you wash it's best to add a drop or two of a light oil (apricot, sunflower, safflower) to the area, which helps dissolve the extra oil when it forms. If it's really bad sometimes it's easiest to shave the areas so you can wash easier.
Also, there is a condition called feline hyperestesia that is often mistaken for itching/grooming. Usually you'll notice repetitive behaviors and skin rippling. Look for videos on youtube.
