Couple of 7 day car rental codes from main EA forum....
Lamborghini Gallardo " TENSOR " : B5WR-SMQW-N639-HUBP
BMW M3 GTR : 7YQB-798W-KDJK-DVXS
These may only show up in the boost store gift section from in the game versus the website or for free from the car dealer. Also, these will not work if you already have the car in your gifts from a previous promotion unless you use the old one first.