I ran a Tom's kit with Evol R shocks last year on my 174. It is a great skid and rides really well. It doesn't get up on the snow like a KMod will however and will not control front end lift on a turbo sled like the KMod either. I let Tom talk me into Evols after swearing I would never do another set of air shocks a few years ago. Tom is GREAT to work with and did everything asked of him and then some, he even overnighted me a set of ski shocks with new valving in them after a known warranty issue with Fox so I wouldn't miss a day on the snow. I highly recommend Tom's Snowmobile and his emotion rear skid kit for anyone looking to upgrade the stock skid on a stock hp sled.
HOWEVER, if you are running any kind of power enhanced sled, ESPECIALLY on a shorter track sled, the KMod is superior in both getting up on the snow and staying there while also giving you the ability to control the ski lift when pulling steep inclines. Yes the KMod is more expensive, BUT, look at what you are getting for your $25-2600 dollars. High quality COILOVER shocks that are EASY to make adjustments to on the mountain and get them tuned to your liking... and once tuned they stay there no matter what elevation changes you make. In order for an air shock to do this you would need to fill them with nitrogen to keep the pressures consistent over a wide range of elevations. You also get Iceage rails, with a better approach angle and no tip up at the rear, anodized to keep snow off of them if you choose, and are far stronger than the stock rails. You get a far superior skid GEOMETRY, not an overworked, albeit much better riding, version of the stock skid. If you choose to do so you can also sell your complete stock skid (should bring 800-1000 or more on the open market for someone looking for an upgrade to tmotion) which brings your overall investment down to around $1600-$1800 for a complete KMod.
Again, I can't say enough great things about Tom and his emotion kit. It works great and he is excellent to deal with. But for someone looking for that ultimate in performance and ride, the KMod is just better all around. And I've owned and ridden them both for more than just a spin around the parking lot. This is just my opinion based on my OWN experience, sorry if it offends anyone.
I guess both my BoonDocker turbo'd XMs can't make the crazy HP your Impulse makes. Ski lift was never a problem on either of my turbo sleds. Convincing a spring guy to go air shocks is like convincing a Bernie Sanders supporter to vote Trump