As others have said, check the eBay Twintercooler thread and look around for some install tips. Apparently the hoses going to the stock IC on this version can be a bit oversized, so you may need to buy a small piece of hose and "stack" it. See
https://www.golfmk7.com/forums/index.php?threads/ebay-twintercooler.354522/
But yeah, for around $200 this pretty much can't be beat. Hell, bring him $150 and see if he'll bite. I'd be willing to bet you'd like this intercooler, and will certainly will notice a nice increase in power, especially during warmer months. That is, unless you plan on a big turbo, or are just looking for the absolute best unit available, do multiple back-to-back runs, track the car, etc., in which case I'd say get ready to shell out the $800 or whatever for a high end stock location replacement, not to mention all the cussing you'll do during the install.
I bought the Forge Twintercooler clone off eBay before the Mabotech clone was released, and for what it is, I love it. It was a cheap, great upgrade over stock, and was MUCH easier to install than a stock location IC (I do not want to do one of the stock location jobs again). At full throttle, temps drop rapidly to 10-15 degrees or so from ambient, sometimes even less, even after a handful of back-to-back runs. That's on an IS20 with a 5150 tune (27-28ish psi on e40), and the stock downpipe. It netted me 0.2-0.3 sec and 2-3 mph at the strip, so probably a bit over 20 hp, give or take.