take your grips off and TAPE THE HELL out of your bars where the grips go.(with electrical tape, or if you dont have that, just use masking tape or even duct tape) Make sure there's a lot of tape. Then hairspray the inside of your grips and bars with hairspray. Grap a paper towel for traction and pull and twist the grips back on to the bar. It'll be reallly hard to get on, but that is a good thing. Your grip will never throttle again.
I ride foamies and foamies only, and do this with every pair. IT WORKS.