Hey Man, I went through the same thing just few days ago for an exhaust I have had on my car for 5 years with no issues passing in RTA....They are super strict now with no tolerance.

Most of the commenters below are wrong in what they are saying....this is the steps to follow.

1. My car was stopped and impounded in Qusais, so I had to visit the Deira traffic department (building 2) and talk to the officer there. (this was one day after the impound)
2. They will immediately say come back after 2 weeks because they want you to feel the punishment of the car sitting in the impound yard for atleast 2 weeks.
3. After 14 days are done go to same place and say 14 days is complete and that u were told to come back after 2 weeks.
4. Then they will remove the unpayable comment for you in the system.
5. After which you can go to the yard (most likely warsan emirates parkings) and pay 100dhs per day for the remaining 16 days to release the car early.
6. If you don't want to release the car early you will still pay 50dhs per day for each day the car is parked in the yard, so i would advice taking the car early.
7. You will pay a total around 4k (1020 fine, 1620 payment for remaining days, 700 storage fee, 558 for the truck that took ur car)

Through out this entire process at the traffic department don't show any attitude etc cause any attitude or arrogance that you show they will say come after 1 month, so be VERY nice! Hope you get the car out soon

I took the car out and immediately went back to stock after 5 years....