Any way to speed up IR?

[Xtreme2damax]

I have two GTX 460's in sli however I'm well aware Dolphin can't utilize sli. If I I lower IR to 1x with everything else on performance settings, unlock fps I can get awesome speed - over 100fps in SMG2 with occasional drops under 100fps. However when I use IR, typically anything above 2x it results in massive slowdowns. I can go from 90fps to 100fps down to 60fps to 70fps, sometimes lower which is a shame since it makes games look nice. My question is there anything I can do from my end to speed up higher IR's or something the devs would eventually be able to do?

My full specifications:

Core i7 950 @ 3.8Ghz
2x GTX 460's in sli.
6GB DDR3 Ram

I usually keep IR on auto (multiple of 640 x 528) using the OGL backend with AA off, AF 16x, EFB to texture, 1080p 16:9 fullscreen resolution, efb scaling on. The settings I use are balanced between performance and compatibility without sacrificing visuals. Typically games stay above 30fps (30fps games) and 60fps (60fps games) regardless of IR with the occasional hiccup/stutter that it will briefly drop the game below 30/60 fps. I thought with the massive performance boost Dolphin received higher IR's would've had less of an impact on performance.

Thanks. I searched but had trouble finding anything, I do vaguely recall similar topics on the subject in the past but can't seem to locate them now.