You can't compare free memory on an 8130 to an 8330. The 8330 has 50% more memory to start with. Have you performed the CrackBerry Memory Optimization Procedure? It's linked in my sig. If you haven't, you probably still have preloaded items that you don't want, wasting your memory.
You have to be at your PC to run the procedure anyway, so it's ok that you can't see it at the moment. When you get to your computer, take a look at it. Reed's procedure may help you find something you've overlooked that you can remove.