While I'm a TCW3 lover for years - either at 640:1 ratio as gasoline additive, random ratio in IDI engines, or 25:1 in two stroke OPE - I now have one TGDI car and I don't use TCW3 in it because I'm afraid of adverse effects.
What I've seen so far while running TCW3:
+Smoother and quicker cold starts
+Less engine noise at idle and low rpms, all loads
+Less motor oil consumption on engines that burns some on decel
+Prevents sticking float valves and other issues on carburators, keeps them clean and free from deposits
-Some setups experiences a slightly lean running condition/behavior at 640:1 ratio, like my friend's bike engine (Kawasaki Vulcan S, an ER6-derived roadster in custom disguise, injected inline-2, with full decat exhaust)
-can be tricky to keep sealed all times, ends up messy before the end of a quart jug