I like Rage3D tweak, but with my 9700 I had problems starting a multiplayer game of BF1942 while using it. Never had a problem with my 8500 or 7500 while using it though. Many times I'd get get lock-ups, crashes, ect. This is with Win98se and not even overclocked, but the tweaker was active.
I alway's just install the Overclocker, nothing else. You could be seeing a drop because something like Ansio filtering is auto enabled , or something like that Maybe?.