dude, I had this problem, but I was able to fix it, but it only works with rubber grips.
1. remove your grips
2. clean your bars with windex and a clean rag
3. boil your grips for about 8 minutes to remove all excess greace and oil.
4. wrap your bars in glossy brown packing tape, only on the part where the
grips will be (thin layers, unless you want bigger grips)
5. squeeze the tape tightly on the bars and allow it to bond to the bar.
6. put the grips back on using only the heat from the boiled grips.
7. squeeze the grips tightly to shape your grip how ever you would like.
8. let the grips cool down and bond to the bars
9. this should get rid of the throttle grip almost completely.