As far as I know the Riva is the same as stock except it has an adjustable rev limiter. My 96 came with one but I swapped it out for an MSD when it wouldn't fire the ski anymore. Most CDI's get the blame for a weak or failing stator and should be shelved instead of thrown out because usually something else goes out right after you've tossed them away.
I've run Enhancers in all my skis but decided to bypass the Advent T3 I had purchased for my build and bump up to the ATP EPIC for my X-Scream SS865 and I couldn't be happier. From easier starting and awesome hit right off the bottom to ease of programming I think the EPIC is a no brainer. I'm considering purchasing a second unit for my Wife's ski before Chris realizes that he's selling them too cheap and bumps the price up. :biggrin:
I'd buy the ATP EPIC just for the customer support.