I've just bought one of those Evolve kits after reading up on them... ZDSPB reckon that it doesn't matter which type of HE bolt kit you get, most will increase efficiency by 40% which sounds pretty impressive and makes you question why it took so long for Smart Parts to solve the problem themselves.
Personally I'd avoid the evolve one, it's a pain. No better efficiency than stock but no parts are copmatible (well maybe the guide with stock parts. I'm still awaiting the eigen bolt that has been coming out for 4/5 years but should be close (in final machining)
It's a LP can, personally I don't bother with them, but then again I don't have a shocker I can use them with. Lower pressure is always nice. I offloaded just about all my shocker stuff over the last year, so don't have one (or much of anything really) spare, not that I owned one in the first place.