I had the same problems I went to Adam tune and he solve issue
https://adamtuned.com/collections/2015-ecoboost-mustang/products/upr-dual-valve-catch-can-2015-ecoboost-mustang-smoke-fix
Go here this solved my problem with white smoke.
https://adamtuned.com/collections/2015-ecoboost-mustang/products/upr-dual-valve-catch-can-2015-ecoboost-mustang-smoke-fix
Ford didn't help me at all. So I did some research and this is what I came up with. Got it and had it put in Two days ago and no more white smoke.
https://adamtuned.com/collections/2015-ecoboost-mustang/products/upr-dual-valve-catch-can-2015-ecoboost-mustang-smoke-fix
I went here because I had the same problem. Had it put in two days ago no more issuses.
https://adamtuned.com/collections/2015-ecoboost-mustang/products/upr-dual-valve-catch-can-2015-ecoboost-mustang-smoke-fix
Check out this site it help me. I had in put in my 2015 mustang two days ago no more problems. https://adamtuned.com/collections/2015-ecoboost-mustang/products/upr-dual-valve-catch-can-2015-ecoboost-mustang-smoke-fix