Here's two pictures from the thread "Weighed the Viper 162" by user jrusher a few links down.
The first picture is a 2015 Viper Mountain turbo with a 180hp kit, full tank of fuel and ready to ride, Mountain fit hood, lightweight exhaust option and a lightweight battery at 606 pounds.
The second picture is a turbo Pro with electric start and 3" track at 601 pounds.
You could lose the starter on the Pro and save some weight (that isn't an option with the Viper), but it shows an apples to apples comparison. I'd say that the Viper is in the ballpark anyway. And there's a pretty good chance that that Viper will still be running 10 years from now with 10 or 15,000 miles on it.
The Yamaha/MPI turbo doesn't void the warranty either. 180 horsepower with a full warranty is a good thing. I have a friend who is a Ski-Doo guy and he gets about $5000 of motor work done to his 800 XP and says that it's supposed to make 185 hp. The only problem is that he grenades an engine just about every season and the warranty is void due to the engine work. Then he buys a new motor and sends it off to get it to make 185 hp and expects to get about 1000 miles out of it. He was telling me about blowing up his motor at the end of last season and having to drop big money to replace it. I told him about the boosted Viper MTX. His first response was "But they're so heavy" (this coming from a guy that has never ridden a four stroke Yamaha in the first place). I gave him the run down about the Viper is supposed to be lighter and a better mountain chassis and that he wouldn't have to replace the motor every season. He's a Doo guy, so I wouldn't expect him to jump on the band wagon right away, but it sparked his interest. I bet he'd be more interested if there was a boosted Viper around for him to test ride. Unfortunately, the nearest Yamaha dealer is about 250 miles away in Canada, so it's not easy to test ride one around here.
So, if you are into a sled that will perform well and not have to be towed out so often, it would be worth considering. Wish I could afford one. Maybe next year.