I've had the same problem with these units ever since I began receiving them. GPU use never reaches higher than 80%-81%. Both times I ran one on an old GT 430 and then I upgraded to the GTX 560 Ti. Both cards never even got close to 99% Frame times decreased and far higher PPD because of the more powerful GTX. Several other posts have the same thing happening. It is most likely the PCI-E bandwidth speed not being able to keep up with the amount of data created by the GPU. Overclocking will make this even worse, although the frame times can be decreased with more MHz. What sounds silly is what works. Actually down-clock to the speeds of a lower end card. Keep in mind this is my own experiment and even I'm not going to continue this method after this post. I'm running at 500mhz gpu, 525mhz memory, 1000 MHz shader clock, and 1.087 voltage. With a GTX 560 Ti... I'm getting up to 88% usage out of the GPU as apposed to 80% or less. The frame time and the PPD both suffer from this so I don' really think it is worth it just to get the extra use percentage increase. Basically the data is being created slower so the bus can move it. Like a funnel or hourglass effect.