I know this is completely random for a DA journal.. But I thought it'd be the best place to find help

I'm trying out the new ICEnhancer for GTA IV:
[link]And I've successfully installed it and it looks great! But I have a problem, the game is lagging majorly! Everything is moving really slow and I can barely take a few steps.. I have a feeling it's something to do with Steam.. It was still kind of slow when I fired up GTA IV before the ICEnhancer.. And I have a good graphics card (1GB) and also, when I pause the game there is no text in the display, it's invisible!
Does anyone know what my problem might be? Any help would be appreciated, I'd love to be able to play the game without lag

Thanks
-Pat