I'd suggest to use asynchronous paging for this type of usage. As TTIWAdvWebGrid has a significant amount of more cell level capabilities, this unfortunately has the side effect that a cell involves more HTML code than the basic cell from TIWGrid. If you do not want to use async paging, we'd really need to have a look at the formatting of your columns / cells to see if there are things that can be further optimized.
I will check out the async paging and see what kind of results I get... all of the columns in the grid are normal although I am using column header sorting.