Alpine turbo
Well I'm no expert on the turbo thing. Installed a few on two stroke and own a Nytro with an Alpine front mount. My setup runs 10 - 18 lbs boost. Could run more with engine mods. Honestly... I ran 10 lbs on pump gas at 240 hp most of last season with no hitches. The Alpine front mount is snappy and strong. For a guy who likes to play hard but doesn't do the video/crazy chutes where it is do or die, the torque and 240 hp is lots. If you wanna climb the crazy stuff 15 lbs puts you over 300 hp at 50/50 premium/race fuel. I know a couple guys who run av gas instead. I have no experience with av gas and 4 stroke turbo's myself, but I know it has been a cheap alternative to race fuel for us goofs running super 2 strokes that need over 100 octane. Still, ya gotta pack it to the hill. It is a lot cheaper, I think I was around $1.40 ish last winter.
If you want silly power crank the dial and run straight race fuel at 18 lbs. This is supposed to pull 385 hp. I never ran mine this high. I tested the 15 lbs and ran 50% c-12. On the flats I can't say you would notice the difference. On the steep, yep it will rock your world. I ran with the rear mount guys and I've ridden the front mounts and my preference leans to the front mount. It seems quicker when you squeeze the throttle. I think overall the rear mounts vs front mounts when spooled are close. Mine has a slight hesitation on the very bottom right at clutch engagement. This is caused by the CPU transition. The sled idles on the stock cpu and switches over as you come off idle. Not an issue as it is gone when the clutch is engaged.
If you are looking at a carb model, you have to remember that you have to pause when you back off and get back into the throttle. I am not 100% sure why this works this way but a bud has an RX 1 and it will stall if you back off and hit it. Just something to think about. Fuel injection is the way to fly these days if you can afford it. No more jetting... blah... blah. Just easier overall, and can add propane easy.
As far as fuel economy goes. My sled at 10 lbs ran with the rest of the pack. I never had an issue with fuel economy. The more boost, the more fuel. I know a few running 15+ lbs that pack 20 liter jerry cans to go where we go. Guess thats a choice you must make. Propane is a bit on the hard side if you run out. In my group there is always extra fuel but propane is pretty scarce. If I'm low, I can dial the boost down and run premium. Propane... well pretty much self explanitory.
Hope this was informative. If you have any more questions let me know. Oh yeah... Alpine and CR racing both have lots of experience with this stuff, check out their websites. CR is running some propane stuff and I think a couple Alpines customers are too.
Later:
D