Nath stay away from the varex its simply cheap china rubbish.
Restricting your exhaust is going to hurt performance but it certainly wont hurt the engine.
have you thought about finding a good fabricator to make a restrictor that you can bolt in when you wish to take the family out but can remove when you want to beat up on it ?
bolt in restrictors are not legal as they must be riveted in place but so are the varex style mufflers and well lets face it if a copper with a good understanding of what a subaru should have under the bonnet it would be the least of your worries
