Ok, I'll respond with as mature an attitude as I can; 99% of the sh*t you can read on t'internet about 'airsoft gun upgrades' is a load of wank. The vast majority of it's written by 14 year old kids who still cling to the idea that a longer tighter barrel is more accurate and that LiPo batteries will scorch your trigger contacts in minutes so you MUST have a MOSFET or your gun will break.
All false.
If you want good consistency at range (note; not accuracy, there's no such thing as an accurate airsoft gun, just consistent ones) squeeze out the maximum FPS your site allows and get your hop up working perfectly. The FPS isn't a MUST HAVE, but a good hop-up is. Since I don't know what brand your gun is I can't advise you on what to do to improve your hop up, but a standard tokyo marui hop up unit and rubber is always a pretty safe bet.
With barrels quality of finish is more important than bore diameter or length, a 100mm long 6.08mm diameter barrel with a flawless inside will be more consistent than a 600mm long 6.03mm diameter barrel with even a tiny imperfection.
MOSFETs have a place, certainly the more expensive computerised ones which provide all sorts of awesome features, but even the standard pure-MOSFET that just routes power past the trigger contacts is useful... if there's a problem which requires it. If it aint broke, don't fix it is a mantra I pretty much live by. If your trigger contacts haven't burned out, they aren't broken. I personally don't advocate the use of 11.1v batteries in anything really, there's no need for 25+ rounds per second monsters and the added wear from the increased cycle speed will wear the gun out quicker. Use a 7.4v LiPo and you'll get the advantage of a higher burst discharge rate than NiMh meaning your semi-auto trigger response will be quicker without the trigger contacts burning out and your piston stripping because the whole thing's cycling at a million miles an hour.
Short story:
If there's a particular aspect of your gun's performance that you feel is lacking then there is a way to fix that problem, however, throwing parts at it as 'upgrades' because on the internet everyone has an upgraded gun is at best a money pit, at worst a good way to screw the gun up.