Is there a consensus as to when the stock TIP is a restriction? is38 and up?Honestly, I can't justify the cost. It's a metal 90* elbow, that like you said, can't even be proven matters. Sure, Jeff did all the testing to show which ones flow more air, but as far as I'm aware, there hasn't been any actual testing that the stock TIP is a restriction to an IS20, even when tuned.
If anything, I'd drop the stock on back on for now, get rid of my v1 CTS one in the classifieds, and add a little more money to get the v2 CTS one as it's the cheapest available, and looks to have rectified the angled connector that would cause the upgraded breather hose to not work.
While I'm not an advocate of "get the cheapest one available" for many things, like I said, it's a metal 90* elbow, and really doesn't have much room for failure.