I'd say toss. With 99 base speed, you're not outrunning much in a trick room. Yveltal can't even set up the trick room itself.Since I haven't gotten a response to this,
Keep or toss?
Relaxed XYZ Yveltal 31/30/31/31/31/03
Does this have any use/trade value whatsoever? I feel like I'd be better off resetting for something else but I'd like to get some opinions.