Hi Tina.
When you undid the 3 screws & lifted off the top did you only clean the large oppening ?
If yes then you still have not done enough to get maximum air flow.
You need to clean out each vortex tube.
You didnt mention the pre motor filter this is the one on the side with foam in side it.
Wash this with soap & hot water both parts use a paint brush to scrub white filter (do not use any other type of brush the bristles will be to hard).
To check white filter is clean hold up to the light if you can see dark patches it is still clogged use lots of soap or try using carpet shampoo & scrub again with paint brush this disolves all the impregnated crap.
If you still having problems let me know.
http://dysonmanuals.inc.io/
chris
September 2007