[Hozu]

Shadow Boosts seem to be just a level boost as implied by the game (ie. lv 34+), rather than a seemingly random set stat increase. When I was looking at Hypno I've noticed that the actual stats always match the stats that it would have at level 37 for the given IVs/Nature even though it's actually at level 34.

Now if I had only thought to check by level earlier... I had only thought about it when I saw that Natu's boost was really low because it had a -Speed nature and a very low Speed IV. Anyways I will post the level boosts as I go:

Poochyena - +1
Duskull - +3
Mawile - +3
Snorunt - +3
Natu - +3
Lunatone - +3
Hypno - +3
Sableye - +3
Dodrio - +3
Banette - +2
Magmar - +3
Pinsir - +3
Rapidash - +1
Lickitung - +3
Scyther - +3
Chansey - +3
Solrock - +3
Swellow - +3
Electabuzz - +3
Snorlax - +3
Mr. Mime - +3
Salamence - +1
Marowak - +3
Lugia - +3
Rhydon - +1
Moltres - +0
Exeggutor - +1
Tauros - +1
Articuno - +0
Zapdos - +0
Dragonite - +2

Example - Say you encounter Lugia and it has hex-flawless IVs and is Timid nature. It's level boost is +3 so calculating the stats for level 53 yields stats of 191/104/159/116/184/151 for when you're battling against it, but when you capture it the stats would be 181/99/150/110/174/143.

To check the boosts yourself it is pretty much the same method as before. You would catch a pokemon when it speed ties one of yours so you know the exact speed it has. Then figure out the exact speed IV. Then figure out what level it would have to be to have the speed it had given the speed IV and nature and subtract the level it actually was to find the boost.

Turns out that some of Greevil's pokemon DO have a shadow boost. Just not the Kanto birds.

I would really like other people to test these as well as I would like to know if these level boosts are always the same across other files. Some of my results lead me to believing that the boosts are always the same for each pokemon.

If anyone wants a Pokémon that I don't have listed let me know.

Edit: Added Snorunt