So I am a boosted Apex guy but had a Nitrous RX1 back in the day and wanted to boost it so I have some 10 year old knowledge so take that for what it's worth.
Carb hats can leak so back in the day many swapped out for aluminum billet ones.
If its a built engine you NEED to understand the compression ratio to understand the fuel to use. Its not uncommon high elevation guys running splash of race fuel with premium on stock compression, you do that down here you will blow the motor. You have to lower compression to run higher boost levels. So 5 psi is fine stock, go to 10:1 and you can run 10-11 psi, dip into the 9s to get 11-14psi. Every psi is 10 hp so your base motor (before it had any compression removed if they did) is 140hp so 5 psi is another 50 for 190 total. etc. You have to figure out compression,,, it either has a thicker head gasket or lower compression pistons. Maybe scope the bores with the a camera and see if you see get a look at the piston shape and match with a CP. carillo, or wiseco. Unfortunately it will be tough to figure out. Taking a static compression test will be OK but still not conclusive.
The drop and roll chaincase will make the sled feel heavy on the front skis. It will climb out of deep snow better then trenching like stock but it will be a work out. You will need to mess around with rear suspension and possibly even raise the front suspension to help get the sled to lighten the front ski weights.
The boondocker kits are pretty well known to cook and ruin the mag cylinder, they don't like all that heat over there. Also the oil tank is not as ideal as stock so some have experienced oiling issues and spun bearings because of it. Try some thermal management in that area with heat shielding, heat tape, etc, you can't overdue it, to get it to last. Also the log type header can get hot and crack. So inspect everything real close, take the gas tank off and look at all the exhaust and black residue for leaks.
Lastly tuning ugh this is why I didn't go with a boosted RX1 and went to the apex where I tap keys on a controller to adjust fueling, with the carbs you got 4 of them damn things and the pilot jets plug so easily. The mains are easy, you generally use a rising rate fuel pressure regulator and that keeps them in line at WOT. It's the needles, and middle jets that constantly need adjustment or it will bog, fart, bang, in different temps. Its works in the mountains where people generally go up on days that are consistent temps, altitude, etc. In the midwest we ride in -30 or rain for cry eye LOL.
So make sure that AFR gauge is working well, I can't get a sensor to last more than 2 seasons. The AEM will show dashes when it go bad but just before it makes bad readings that make you scratch your head, so when you start tuning start with a fresh sensor. Go back in the forced induction pages for some RX1 jetting guides some people were using. Also look for some compensators you can add to the carbs I forget what they are called but companies like Holtzman I think it was something a UFO?? that would allow you the ability to make a little adjustment to the carbs, otherwise pulling them on and off is not fun, I think you can adjust the needle heights from the top IIRC.
Good luck, sweet sled when you get her dialed it.
