Al what it is doing is putting a layer of clean filtered air between the fresh fuel mix in the crankcase and the left over ex gases in the combustion chamber, so the air scavenges the ex out and holds the fuel back for the fraction of a second it takes to let the piston come up and close the ex port. Now the fuel comes in and it doesn't leak out of the ex port as scavenge loss of unburnt fuel. The ex is measured in a dyno lab and a number is calculated as grams per kilowatt (or horsepower) hour. So when a MS 440 is tested it comes out at 120 g/kWh, and the MS 441 comes in at 67. So this saw is heavier but has almost the same HP but will cut a bit longer on the same amount of fuel and pollute less which really should matter to us, and I am not a greenie tree hugger but I do still want to be able to run internal combustion engines 20 years from now, so I guess we need to take some responsibility for cleaning our little engines up. The EPA said back in 1996 that one chainsaw put out as much pollution in an hour as 10 cars doing 60 MPH down the highway for an hour, so that is why they put a gun to the indusrty's head and gave them from 96 to 2007 to basically cut the average emissions in half for hand-held engines above 50cc, and smaller engines had to go from about 250 to 50.
This is why most new designs are stratified scavenge models at least as far as STIHL is doing it. The MS 261, 291, 391, 362, and the new 201 all are this way but the newer models are lighter and simpler to work on.
SO back to your 441. If it is tuned correctly and running right it should perform about as well as a 440. If you open up the muffler and fatten up the carb you probably will see a little improvement in performance but I have not tried it myself, but I guarantee you the fuel economy will drop tremendously so you might as well stay with the older saw. The cylinder does have some complex port timing with 6 ports to direct the scavenge air, and the muffler and the dual butterfly carb and the porting are all carefully tuned as a system.
Make sure the saw does not have any air leaks or fuel system troubles and try tuning it like this:
Gently warm it up. With a tach set the idle to about 3300 RPM, then find the lean drop off point with the L screw. That is where the RPM drops off lean if you go clockwise any further, and also starts to drop off when you go rich by turning the L screw out. Once you find the L screw lean drop off point and the idle is at 3300, then use the L screw to fatten up the idle to get to the desired idle speed of 2800 RPM, not the idle speed screw. Once you get that done you will find that the saw idles well and will have crisp throttle response and is at it's optimum mixture setting for idle and off idle. Then go to wide open throttle (WOT) just long enough to see what the tach says, don't hold it there very long, and go from rich towards lean to get to no higher that 13,500. The module will take away every 8th spark above that so you can get too lean but it won't over-rev, so always go from rich, say around 11 or 12 K up to 13,500. If the carb doesn't tune sensitively then there is a fault in the carb or an air leak or something else wrong. When I tune a 441 this way it runs good, so try it and see if the man has any better luck.
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