OK, I just looked at that kit. Nice enough kit at a reasonable price, but from what I can see, it just converts a TS9 to TS-808 specs, adds some higher quality caps, and an IC socket to be able to change opamps. It does nothing that I can see to change the pedal gain, so if you want more "oomph" from your TS, this won't do it.
BTW, the very popular so-called "brown mod" has two elements to it: First, it changes the ratings of two resistors in the pedal's output buffer to be the same as what was/is used in the TS-808. Fair enough, because many people seem to agree that the 808 has a somewhat nicer/warmer tone than the 9 versions. And the only difference between a TS-808 and a TS-9 is those two resistors and maybe (not always!) a better opamp.
Secondly, it uses "carbon comp" resistors for that purpose, vs. the newer & more commonly used carbon film or metal film varieties. In point of fact, the old carbon comp technology is clearly inferior to these new types, being intrinsically noisier, but this was the type in use when the TS-808 first came out in the late 70's. IMO, this element of the "brown mod" is unscientific mumbo-jumbo. Why upgrade the caps to higher fidelity versions and at the same time install "lower-fi" resistors?? Just silly, if you ask me. But this is the kind of "lore" that floats around and people grab onto as being fact, rather than applying scientific principles and/or the brain God gave them. OK, back off the soapbox. In any case, Monte isn't responsible for the brown mod myth, he's just offering a kit that contains a very popular mod that people look for....