Is it normal for RO to have slow

You system is plumbed incorrectly and will never work as is.

Follow the diagram I have linked to here for the correct plumbing arrangement:
http://www.spectrapure.com/huds/3-STAGE-DWK-RO-NAG.pdf

Note the yellow line is the waste line and it should not be hooked to the autoshutoff valve as you have pictured, it goes to the drain and is where the flow restrictor should be located if you had one. You can always tell the waste line even if it is not yellow, it is on the end of the RO housing with two lines coming out and always the one closest to the outside edge of the housing with the other blue line, the treated water line closer to the centerline of the housing. The black line on the opposite end should be leading up from the carbon block to the membrane housing.


If you bought a Spectrapure 90 GPD membrane the flow restrictor you unit is supposed to have is incorrect, it was originally a 100 GPD system while the Spectrapure 90 GPD is similar to a 75 GPD membrane not 100.
\You will find the correct capillary tube flow restrictor on the Spectrapure website for $5, FR-90, or you could have been able to order the membrane and restrictor as a package when you bought yours.
Follow the instructions included with the flow restrictor on how to measure your waste ratio and how to trim the restrictor for your exact water conditions.

Its easy, you will get it right in no time once you have the correct parts and it is plumbed correctly.

 

UPDATE:

I finally found that I did not have a flow strictor at all. Spectrapure sent me one at no charge and apologized... I followed the diagram AZDesertRat posted and after setting the flow restictor I have a 4:1 ratio of bad and good water with a TDS of 0 coming out of the DI.. My pressure is 80 and TDS straight from RO is 2 so I guess everything is wirking well.. Thanks for the suggestions and help to everyone especially AZDesertRat....

 

glad everything worked out.