The idea of trying to suck more air into the engine naturally sounds interesting, do you have any more info on that? or a place i could get started researching at?
What you said makes a lot of sense though as far as not finding as much information on the topic assuming i were to go forward with this, do you know how the 2 pulses from the tuned exhaust effect the turbo? I came across someone mentioning that the tuned 2 stroke exhaust can do some weird things to a turbo as far as the pulses go, like rotating the intake fan thing backwards. I do not know the technical words for what i am trying to describe, sorry
The 600 HO which is pretty much the identical engine for both carb and SDI is already a fantastic start. A stroker is a common mod for added power, and that is what a 600 HO is already with a square bore/stroke. It also has the carbs or throttle bodies sized for around 8000 rpm, as well as an airbox and tuned pipe for the same rpm. I think that this engine has become so common that we have been sensitized to its amazing power output. It's actually detuned for a consumer sled, but still remarkably strong. It's a jack rabbit.
Just remember the carb version doesn't have a Knock Sensor so it can only be uptuned so much before it becomes risky with pump gas. Most of them don't have a DPM, so they are never in tune. I have ridden one with the optimized jetting and it was quick. Unfortunately it detonated on 87 octane (not me with on it). I am ok with a carb having a DPM, but it doesn't interest me to be tuning a trail 600HO carb without one because it is never in tune. I used to make the carb adjustments on race sleds, but now I am trail riding and have no time nor desire to messing with jetting. If it has no DPM then I jet for -20C and suffer the power loss when it gets warmer.
The 600HO also has triple exhaust ports which isn't a small thing! Like I mentioned, we are sensitized because they are the most common and prolific snowmobile engine in history and a big part of bringing BRP to the top even despite the Isoflex which actually works. Those triple ports are very special. Unlike the E-TEC version, there is nothing restricting the auxiliary exhaust ports. So you have all the exhaust flow that you need.
In Post #7 I provided an important key, power per CC. Those aren't just numbers. It reflects the amount of power that is drawn out of the engine. With a stock tune it doesn't reach much above 0.19 Hp/cc. How about reaching 0.2 or even 0.21 Hp/cc? That is the part that you asked me about, trying to suck more air. The question that I keep asking myself, why would I invest thousands of dollars in a turbo when I can reach 0.21 Naturally Aspirated? One of them is easy. The other is complicated and holds a higher risk.
Now we get into airflow. When looking at the MY2007 800R or the 1000 SDI or the latest version of the 600HO - the 600R - they all have two things in common, W type reed valves and a short reed boot. Both of your 600s have the short reed boot, so you are half way there.
Last is the best bang for the buck power increase. Most common answer is a clutch kit. It is sorta right, but not even close. I have had many pros in the racing circuit tell me to avoid focusing too much attention on the engine. They are somewhat right, but they are also assuming the engine is running top. The thing that I personally have trouble with is a two stroke running with too much blowby the rings. 130 cranking psi is not what I call a healthy engine. And too much blowby is not good for any part of the engine. The very best bang for the buck power increase is a well running engine that is reliable. Then it reaches into traction, clutching, alignment and gearing with no particular order.
Note that I didn't mention anything special, yet I am spent working only a quarter of that or less. Making sure the engine on an old sled is running top is a huge endeavor. Within an hour I can diagnose a sled far enough to know if I even care to work on it.