I wouldn't ever trust eBay for performance modifications. That's not a kit to make an LSD, I'm guessing that all it does is temporarily lock the diff (until you open it back up and take it out). It's just a terrible way of locking a differential.
Now I'm not going to get into the details of how differentials work, and how LSDs work. But I will tell you that unless you are offroading, you will NEVER need an actual locked differential. Not for drifting, not for racing, not for rallyX. Not for anything. A locked diff is not a limited slip diff, it's a no-slip diff.
Race cars use LSDs, and they are set up to be much weaker than you'd think. The #1 mistake inexperienced people do when tuning a car for track racing (or drifting, or rallying) is set up their LSDs way too strong. Most sports cars that come with factory clutch-type LSDs are setup too strong for real racing/drifting (it is done so to make the car be perceived as more fun to drive, but it actually gives you less control).
I must admit, the w202 would be more awesome with an LSD, however LSDs have downsides. I'd never run a clutch-type in a street car (they cause much more wear of the gears because of the friction modifiers used in LSD gear oils, and 2-way clutch-types can have very sudden and unexpected behaviors to any driver who's never done any racing inside a real race car). Torque-sensing differentials are pretty useless in low-traction situations (because there is an absence of torque to sense), and viscous couplings are inefficient. Unfortunately open diffs are simply the best for street cars. 4matic cars apply the brake to a spinning wheel to simulate an LSD. Despite common belief, this is the practice that makes most sense from an engineering point of view, and it makes Mercedes one of very few makes that can pass the 3-roller test, with only one front wheel with traction (I think Volvo is the only other make that can do this, simply because they use a similar system). Even a car with a transfer case and a locking rear diff would fail this test.
My point is, education. My other point is, street car: open diff, race car: clutch-type LSD, off-road car: locking diffs. Everything else is about being mayor of poserville. We had a massive dump of snow yesterday, and I spent an hour sliding about on my local street with my C220, not once did I get stuck, and not once did I have problem maintaining a completely side-ways skid.
I've read up about wavetrac, I'd love to see it in action, I'm always skeptical of revolutionary differential technology because 99% of the time, it isn't revolutionary.