The easiest way to get more power is to get a different bike.
For example, the Husqvarna 650 single, out of the box, has about twice the KLR650's horsepower. At comparable new MSRP, as well.
I doubt the power increase (if any) from the 22-cent mod is MEASURABLE (a desirable mod anyway, IMHO).
Same for any aftermarket jet kit; again, IMHO.
Now if you REALLY want more power, perform the PCV mod!!!!!!!!! (Just kidding; just kidding!)
A sound approach; big-bore kit (e.g., 685). Even there, and certainly any beyond, I think you enter the realm of DIMINISHING RETURNS, power-wise, on a KLR650.
All above, my opinion only; I respect all contrary ones!