I installed the NA_2 map on a 2 gb san disk ultraII with the .1609 poi's and when I drive down the road the map updates only every five seconds. Unlike when I am on the internal memory it works fine. Why would the sd card work slower or since there is not much memory on the card I should get a bigger one and install all of the files from the internal memory to a bigger sd card. I only have the NA map on the sd card. Thanks.