Just my opinion:
- +2 Dex, -2 Str, -2 Con: They are very quick and agile but are not so strong or hardy.
- Tiny: +2 size bonus to AC, +2 size bonus on attack rolls, +8 hide bonus, needs smaller weapons, smaller weight to be carried
- Speed 20ft., fly 40ft. (perfect): They are quick on the ground and have perfect flying abilities
- +2 racial bonus to Balance, Escape Artist, and Move Silently
- Darkvision 60ft
- Favoured class: Rogue
- Bonus language: Infernal
I dont use a calculator but that may be balanced as a ECL +0. Still not sure if I would allow it. I dont think a race exists that gives 4s, so I reduced your bonuses to 2s. Added a -2 con to compensate for perfect flight and defray advantage of being tiny (which also comes with disadvantages). Added more realistic skill bonuses. Changed see in magical darkness to darkvision, I doubt they see better than the like of drow who live every moment in darkness, and I didnt give them Light Sensitivity.
Edited: +1 version
If youre willing to pay a level, I would suggest:
- +4 Dex, -2 Str, -2 Con: They are very quick and agile but are not so strong or hardy.
- Tiny: +2 size bonus to AC, +2 size bonus on attack rolls, +8 hide bonus, needs smaller weapons, smaller weight to be carried
- Speed 20ft., fly 40ft. (perfect): They are quick on the ground and have perfect flying abilities
- +2 racial bonus to Balance, Escape Artist, and Move Silently
- Darkvision 60ft
- Fire Resistance 5, Cold Resistance 5, Electricity Resistance 5
- Favoured class: Rogue
- Bonus language: Infernal
They pick up the dex bonus you wanted and some imp-like resistances. This I may allow as a PC class, still wary of the equal-to-dwarves/elves/gnomes/etc version.
Technik