winterization or the test but regarding the removal of the outliers in general you can keep the outliers in your testing data set unless you are sure 100% that the outliers can make a hug in no case they can they can be predicted so you can remove them from from your from your test also when you see improvements when you are doing feature engineering and you see some improvement with a new feature how do you know that this feature is important because if you keep the outliers in your testing data maybe with some luck you are predicting