First off let me just say, the whole 2d/low-power 3d/full power 3d power saving system works pretty flawlessly in my experience, and leaving it 'On' (aka 'Adaptive') really should never cause you to lose FPS.
I guess it's easy enough to try this 'max performance' thing in the Control Panel, but I would be shocked as heck if that solves this issue.
OP you keep saying you have a '2d Clock' problem ... have you tried the onscreen display feature of Precision/AB so you can monitor your card's clocks while gaming in real-time? If not, you should try it. I think it's rather unlikely that the actual problem here is the cards failing to go into 3d mode when gaming.
Also, the 'prefer max perf' mode shouldn't stop your cards from going into 2d clocks when no 3d app is running. All it's supposed to do is cause your card to skip over the low-power 3d mode and always use full-power 3d mode when actually running a 3d app.
Does GPU-Z show that your card is running in 16x PCI-Ex mode? Have you made sure that you are not forcing any settings in the NVCP? Frankly, if you were getting 300fps is TF2 before, that strikes me as odd, because I didn't think anyone gets that high of FPS in that game
Why don't you try comparing your performance on some 'known' benchmarks with the perf of others w/similar systems, like 3dMark11 and such? If you get normal scores on tests like these, it's about 99% sure that the problem here is NOT hardware-related.
Lastly, there's virtually no chance this is a PSU problem. A PSU (yours, or anyone elses) won't ever be the cause for a low FPS problem. That's just not a possible symptom of a PSU issue.Edited by brettjv - 5/22/11 at 12:13am