The EFI systems on current powersports vehicles (sleds, dirt bikes, quads, side by sides, etc.) are "open loop" systems. Which means that they monitor certain aspects of what is going into the engine, but not what is coming out. They can compensate for barometric pressure changes (elevation and temperature) and throttle position changes, but not for anything that is changing the amount of airflow into (no mass airflow sensor) or out of the engine (no O2 sensor).
Cars and trucks incorporate these items in a "closed loop" system where the computer adjusts fueling based on what it is seeing coming out of the tailpipe as well as what the air properties are going into the engine. This is what most people expect out of an EFI system. Total compensation for all environmental factors.
The reason powersports vehicles don't use a closed loop system is simple: cost. They are not going to add $500 worth of sensors and additional programming to a machine that is already $10,000+ and are already having a tough time increasing sales numbers. Especially when it satisfies 90% of the people using them. The one thing that will drive this is emission standards. Once they crack down to the point that they can no longer go without monitoring the engine that closely, we will see it. Along with a higher price tag.
As for modifications, some sleds can be modified significantly without altering the mapping and some cannot. M7s had pretty rich stock maps and will take fairly significant modifications without changes. Mine has a head, full single pipe, and a jet restriction in the fuel line to drop the fuel pressure and it runs great. Try adding pipes to a M1000 or the 800 HO motor (like yours) and you will have problems. These engines have much leaner stock fuel mapping to comply with EPA regulations.
If you do plan on modding, check with whatever company you are planning on getting the parts from and see which fuel system they recommend. If you have what they use, then they are going to be able to help you out a little more with extra tuning if it is needed. I like the way the dynojet system works on my sled. Very fine adjustment capability to get the fuel (and timing if you have that option) dialed in. Problem is that you need to plug it in to a computer to make the adjustments so field tuning is not as easy. I would still rather pack a laptop in a backpack than deal with changing jets on the mountain though. At this point most companies have maps setup that you can download and use without any issues. Boondocker boxes are better than they used to be for increments of adjustment and can be changed in the field. Both the dynojet and boondocker systems have adjustments based on RPM at different throttle positions. All of the Dobek designed boxes are field adjustable and use colored lights that represent low, mid, and high rpm fueling requirements. Similar to pilot, needle, and main jet adjustments. Some guys like these because they understand that concept and can get them to work ok for them. I personally don't like them as much because they are purely RPM based and don't take throttle position into account. Carbs take throttle position into account with slide cutaway and needle taper.
