now idk if i would call it an "engine sputter" i would like to think its tensioner. i am also running stock belt.

here is another vid inside engine compartment, shot when doing vid above
https://www.youtube.com/watch?v=OZ6u8OzWUw8

and another vid with belt off
https://www.youtube.com/watch?v=kKuIaPny8ZI

sounds fine with sc belt off. i think
also i cant find a vid of a bad gtp sc tensioner

flow mod as in down pipe?
i ordered a 3" exhaust from zzp down pipe back just waiting for that than i was gonna get it tuned