I can tell you I am jones'ing for a new Viper 162. I am one of those, build it, bored with it, sell it kind of riders. Some sleds I have owned....2014 Pro Lite 153, 2010 M8 162 925 w/push race gas turbo, 2011 Doo 1200 mcx turbo 163,2009 IQR Carls 660 big bore 151, 2010 Apex Alpine Turbo 162, 2005 Vector powderlites/Alpine 163, 2007 RMK 700 155. Here's my breakdown for what it is worth.
2 stroke, light, fun, lots of work to keep a modded one on the snow. Proper wrench time will equal good hill times.
4 stroke, heavier only when stuck, lots of fun, anything less than 400hp is a turn the key and ride sled if put together by someone who knows what they are doing. Drive chains have been a downfall of the turbo 4stroke, much like tranys on hopped up diesels. If you don't go to a belt drive, change the chain/sprockets before every season for piece of mind. Even with belt drive, I would probably change after the first year, just because I hate to be towed.
Favourite sled in tight trees, Pro lite, turns on a dime. I have ridden the 162 Pro Lite, feels almost the same. You can set up a Viper to turn the same, probably better because of a little higher CoG.
I have spent time on a Boost-it 174 Viper. Loved it except for two things. 2014, so the lay down post is terrible, and the big a$$ trail seat. both taken care of for 2015. I haven't ridden any other Viper turbo other than the Boost-It kit, I can say I was very impressed with that kit.
Before I spent thousands lightening up a sled that really doesn't need it, I would swap the front suspension of the Viper. Either Skinz or BDX would be the best choice in my mind. I have ridden both, and both improve an already great chassis. Ski's, it needs them, my choice is powder pros, but that is very personal. Boards, tube boards, your preference.
I say go for the change. the chassis and engine are both great. once you ride 4stroke torque, even going to a well built, fast 2 stroke, you will miss the grunt.
