One of the first things to consider replacing would be the silencer (if this is legal where you live).
The stock unit is quite heavy and replacing it with a aftermarket unit could easily save 8 pounds.
Removing the mud guards will reduce weight but if you ride in the wet it may not be the best idea.
Removing the tool boxes saves a few pounds but it exposes a lot of important electrical equipment to the elements. Not a good idea on a computerized fuel injected bike.
Removing the air filter is (IMO) being pennywise and pound foolish.
Yes it might save a pound or so but your engine will be breathing dirt which will rapidly wear out the piston, piston rings and cylinder bore.
Your Royal Enfield is an old fashioned motorcycle with a newly designed engine in it.
That redesign increased the horsepower about 27 percent but as you've found, the machine is still far from a crotch rocket.
Ace (a forum member) is working on developing parts that will greatly increase the horsepower but it comes with a large price and a complete rebuild of the engine (whenever he finally gets it ready for release).
My suggestion is to just ride and enjoy the RE for what it is. A true classic in the old British style.
It's dependable. It gets great fuel economy and any oldtimer who can remember his early years will instantly become friendly.