Mod is shorty for Modify... as in to alter your car in anyway.,.
like the yahoos up by me... they go as far as only doing Sticker Mods...
they think a Holly Carb sticker adds HP.
but I digress
back to your point...
Visually enhancing or enhancing the performance.
if you have Visual as a point of interest, then you must include Acustic as one, Eyes and Ears go hand in hand.
As Emma pointed out earlier today or yesterday.... Cutouts do add HP.
lets restriction means more hp. You are bypassing the entire exhaust
i think emma said she gained 10hp.