1. I need to have had my car for 30 days for approval (i.e. to get approval). 2. I need to have my car for 30 days for approval.
I would say that both are fine.
When you say #1, it implies that you haven't yet got approval. It relates the 'needing to have' to the time of approval. You may or may not have had the car for 30 days.
Aside from the apparent nonsense of an approval (of whom? about what?) being dependent upon having a car for 30 days, the difference between these (correct) sentences is as follows.
The first sentence contains a suggestion that the 30-day period is yet to be completed, by way of explaining why approval has not yet been forthcoming.