The Vonnen Shadow Drive system of aftermarket hybrid power addition for 991 and 981 Porsches (as well as 997.2 and 987.2) is as seamless as it is incredible. With an extra 150 horsepower and 150 lb-ft of torque added to your Porsche, while not affecting your tailpipe emissions or fuel economy in the least, this hybrid system adds all kinds of fun to your fast driving with none of the downsides of other aftermarket power adders. If you don't want to deal with things like superchargers, aftermarket turbo setups, or wild ECU tunes which may harm your Porsche's longevity, but you're still looking for a bit extra power, the Shadow Drive might be your move.
I have driven this system before, and it is incredibly versatile and way too much fun. That said, it is incredibly expensive at $75,000 installed. Is that price worth it to you? If you're the kind of cost-not-an-object Porsche collector, then you probably need to have one. I am not particularly wealthy myself, but even I have considered a way to get myself one of these Vonnen hybrid 991s as a daily driver. It's that good.
The folks at Vonnen recently had Matt Farah of The Smoking Tire in the driver's seat. He found much of the same characteristics as I did. Most importantly, Farah has driven just about every car on earth and he found this hybrid 911 to be fun and interesting, which is a feat in and of itself.
The one thing I will say that Farah didn't, I actually found Vonnen's "Street" mode to be much more fun than "Sport" as the hybrid assist comes in at a lower point in the throttle's travel. In that way, you're able to dip into the artificial electric boost earlier in the rev range and it adds to the seat-of-the-pants speed sensation. It's a truly incredible machine and a great driving experience. If you have the means, absolutely get one. Don't wait for some distant future, be part of the future right now.