My gps doesnt show all the streets - Garmin nuvi 1490T GPS Receiver

Sometimes it will not all the streets, especially main streets, unless is zoomed in, try the zoom feature in and out, or three 3 d or 2 d feature.

No GPS will always show "all the streets". Generally speaking, later versions of the map database software will have more current street data. There is a considerable lag, however, between when physical changes happen (new streets, re-routed streets/roads/highways) and when they appear in GPS map files. If your map file is not up-to-date, this may be the source of your problem. My experience with Garmin's map files is that the newer updates seem to have more outright errors than the older files. Outright errors are not uncommon and Garmin has a facility for you to report errors that you discover.

All of the county road names (numbers) where I live changed over 10 years ago. Garmin's current map file in my 1 year old Nuvi still shows the old numbers. A recent highway re-route, however, displays correctly. It just takes a lot more time for the obscure changes to be reflected by whoever it is that Garmin gets their database information from.