We're excited to announce that we've fully migrated the Xbox Forums to their new home, here on the Microsoft Community forums!
As of today, going to forums.xbox.com will redirect you here to the Xbox area of the Community forums. We've moved all of your existing threads over so you can continue and start conversations with the new forums experience.
We sincerely appreciate the feedback you have provided over this transition and can't wait for you to check out the new Xbox Forums!
I don't think you can go back to that race. You'll need to save up credits to buy the P1, get one gifted by being at level 5 on Forza Rewards. Once you've got one in your garbage - just take it out for a test drive (245 is easy on the straight at LeMans).
You also might be able to find a rivals event that uses the P1 if you don't want to save up to buy it.