Go with Impulse. If you search my posts, I just did an apex impulse install. Paul is awesome to deal with, will talk to you at all hours of the day/night whether it be a weekday or weekend during the install process.
The quality of his parts were great, everything lined up very nicely. He will also give you some pointers when doing the head and stuff that takes a lot of the guess work and trial and error when putting the cams back in.
My next sled will be impulse powered also. He will also preset the fuel controller based on the boost you want to run at the elevation you run. And also knows what to clutch it for.
Not to mention you get the surge tank, which I feel is a big plus, and with the surge tank and new tank you get 12 gallons of fuel. Means no carrying on the back for big rides.