6800GT cooling and temp changes and questions

Ok, here's what my current cooling setup looks like:



I have two 40mm fans modded into the case next to the expansion slots that are currently setup as exhaust. The top blowhole is currently passive (no fan) and there is a 120mm exhaust fan in the back. I also have a medium flow 80mm fan in the front of the case as intake, it blows over the HDD's and toward the video card.

My question is this:
When I tested temps using RTHDRIBL, I kept all case fans at normal speed except for the two 40mm exhaust fans which were turned off (full load GPU temps about 68ºC). Then I tried turning the two 40mm exhaust fans on nearly full speed (about 9cfm each), my video card temps actually go up a couple degrees C (to about 70ºC)! I let them run for a while to make sure the temps stabalize again, then I try turning them back off and the video card temp falls back down a couple degrees! So I know it's the exhaust fans, but what does this mean? Do I need more intake? Should I try switching the 40mm fans to intake?

I also put my hand behind the fans to feel the air they were blowing out, and it was hot air. So I'm really kindof confused here

It's pretty hard to tell which configuration is the best. Sometimes it's problem with intake, sometiems with air circulation. With Zalman design, part of air that went through heatsink is sucked back by fan and passes heatsink again, what's bad for temperatures. So it's possible that turing bottom fans on decreased air exchange in graphics card area. I'd definietly try on or 2 of them as intake or both as exhaust with some additional side panel intake, like with Chieftec LBX cases.