Just Responding your question!! if you buyed your pearl this year you can use a 4gb MicroSD.
If you see on your manual there is no limit of size for MicroSD card and it also have on BB original website.
Im from Brazil using TIM actually and i can use a 4GB fine on my pearl i tested it last month with a kingmax microsd card. but Sandisk is about to open a 4GB microsd too that works like the old 2GB and HC wich will work on your BB.

the picture is attched.