Okay, here's how mods work...
Performance/engine mods-- Make the car go faster. If they are factory built, installed and warranted then they add value. BUT, it's up to the buyer to determine how much extra they are worth. Probably not 100% of original cost unless the mod. is ultra good and very rare.
Appearance mods-- Probably don't add much, considered ricey if they are overdone. The TRD kit is pretty mild and looks pretty good overall, but not worth it IMO.
Handling mods-- Nice according to what you want out of them. Tighter steering, firmer ride, lower stance, etc. Again, up to a buyer to determine what upcharge (if any) there is.
Clear taillights, LED's, loud mufflers, decals, etc are pure crap. They take away value esp. since they are cheap aftermarket junk. I would just say factory manufactured mods CAN add value to a car if done properly and a buyer is out there who wants them.
