if i use not so fast on bomb gear token does it stay on battlefield?

Radiance rules aren't published yet. This uses the printed card and current rules only, and it isn't a ruling on the new mechanics.

Yes, it stays — Not So Fast can't remove the Bomb. Not So Fast only counters an enemy spell or ability that chooses a friendly unit or gear (both conditions on the same clause, FAQ #62), and the effect that plays a Bomb token ("play a Bomb gear token to a battlefield") only picks a battlefield — it never chooses any of your units or gear (FAQ #8673 pattern: choices made by a resolving effect aren't the spell/ability "choosing"). So the Bomb token isn't a legal thing for Not So Fast to counter, and it enters and remains at that battlefield.

Two adjacent notes. The Bomb's own death trigger ("when it dies, deal 2 to an enemy there...") does choose a unit — yours, if you have one there — so Not So Fast can counter that trigger; but that only cancels the 2 damage and the chain-kill of the other Bombs, it doesn't stop the Bomb from dying or bring it back. And Deploy is exactly the "effect specifies otherwise" that lets the Bomb sit at a battlefield instead of being Recalled to Base like normal gear (Rules 149.2/457).

This is my interpretation based on FAQ #62 and Not So Fast's printed text. No official FAQ exists for this specific interaction.