A really cool take on the Advance 2 boost which also doubles as a momentum mod. Pretty neat, though I do have my gripes with it.
It's really odd that it takes far longer for it to trigger than vanilla's Dash Mode (In fact, Metal has both activate alongside each other, at different times), which makes its usability in many of SRB2's levels rather rare. It really benefits from big open spaces where Dash Mode still outclasses it in speed, but it's fine nonetheless.
It's also a bit of a missed opportunity to check if the player has DASH frames for when they enter max boost state. Plenty of mod characters have these, so it'd be a cool detail to include.
Eitherway, great work overall. Welcome Aboard!
As for Metal Sonic + dash mode and the timer being different - yeah that's kind of the point! This is not meant to enhance Metal Sonic's dash mode. Dash mode activates very fast and is an upward speed increase, whereas this is an on/ off constant percentage and works as its own system. It was made for characters who don't have their own dash/ boost modes. That's why it disables with NeoSonic, Blaze, ModernSonic, etc.
I probably should have added Metal Sonic to the exclusion list lol. I also could disable dash mode when used alongside this mod. However, I don't want to make too many rules so adding a console command may be the best bet.
As for the dash frames, almost none of the modded characters I tested use them so it didn't even cross my mind!
It could be a cool effect when the boost activates before dash mode due to a high speed increase, so I will very likely add that in later.
Thanks for the feedback. :)