I purchased the Suby BRZ Horizon Edition from the AH and made a design for it. When I went to share it, the share shows the car in stock. Is this because I need to receive the car thru game play? And if this is the case, will my design ever share correctly on the modified BRZ?
I made a thread about this the other day,seems to be a bug with the game where the design preview is always a stock car,however (for me at least) the car does appear correctly (with bodykits etc) in your personal storefront (pause/community/mystorefront )after a few hours of sharing the design,however some people have noted they still dont display correctly though,but its something to check out 
Thx for the tip. Unfortunately my storefront shows the stock BRZ as well. My last option is to obtain the HE BRZ from a wheelspin and hope that solves the issue.
Just an update - I received the HE BRZ thru a wheelspin and still have the same issue of creating/saving a design and the file saves with the stock version of the BRZ. I figured if I was the original owner that it may work. I’ve trouble shooted every option imaginable from buying multiple HE BRZ’s on the AH, to not painting or tuning it first, toggling the HE body kit, saving in a number of ways. Nothing works for me. I also noticed my other HE version of cars do not save or share as the HE version as well. My last thoughts is it could be account based but I noticed others are sharing 2 designs of the same car and one will display properly and the other won’t. So not sure it’s account based either. Just bad luck with this bug for me I guess.
I have the same issue: some vinyls are shown with no bodykit or standard rims…any news if there is a fix already? Maybe in the way how to save/upload your vinyl? Grts
Unfortunately this is an ongoing issue for Forza games in both the Motorsport and Horizon series and has been for years. It’s been brought to T10’s attention many many times over the years and there has never been a fix put in any of the games for it and no response from T10 with any instruction on how to save designs so that mods will always show. It seems to be random when the mods will show and when they won’t. I shared two designs last night on the same car within 10 minutes of each other … using exactly the same steps … and one shared design shows all body kits, wheels, etc. installed and the other one shows the stock car.
Thank you for the feedback. I have the same issue as you described above. Uploaded several vinyls last night on same and different cars. Some show with bodykit/rims, others without… i think my artworks would sell much better with rims and bodykits visible :)