My motherboard is Intel 945GCNL and it has PCie x16 slot (not the lite version). Also in GPUz it says the card is running PCIe 16x @ x16. So i think my card is working at normal speed as it is not PCie 2.0. But my memory bandwidth is 64GB/s which is less than normal (which is 70GB/s) . But i think that is due to my memory speed being 1000MHz instead of 1100MHz. Some others who have cards with memory speed overclocked to 1310MHz has bandwidth up to 80GB/s.
I think PCIe Lite are special slots on motherboards(some yellow colored ones). It may need compatible cards and mine is one.GPUz doesn't show any other difference from other 250GTS readings.
I definitely know there are PCie Lite slots on certain Motherboards(Got info from net).