Favorite: mugen front splitter
Least: none yet....

 

Favorite: Cobalt XR-2, GTS combo make my track day so much fun.
Least: Hard Dog roll bars. love the bars but hate to install it.

 

Favorite: Full sound system upgrade (money well spend)
Least: I like to always keep my car clean and having a Berlina suck ASS!

 

fav: seat heaters

 

favorite:voodoo knob
least: ???

 

Most Favorite: Modifry Glove Box Organizer
Least Favorite: Invidia V3

 

Favorite- CTSC no doubt

Least favorite - Foose wheels big mistake

 

Favorite: Gendron FSB for auto-x
Least: Replacing front bumper after armadillo

 

Favorites: Rick's X-brace; '06 front bumper cover; Dead pedal; S2000 Stickers to cover airbag warnings

Least favorite: Leather console cover

 

I can't pick just one favorite mod, so ...

Favorites:

AEM V1 CAI (replaced by CTSC/AC)
AxialFlow Engineering Shifter (not recommended for others)
CGlock
CTSC/AC
Eibach Pro Kit
KAAZ 1.5 LSD (not recommended for others)
MaxQData
Redline Shift Beeper

The Aurora ICPC didn't work out the way I'd hoped, and that's the only mod we've made that I didn't enjoy. Hard drives, Windows, and automotive power systems are a bad combination.

Then there are the two mods that I ended up with but never intended to install:

Custom single exhaust, straight pipe with megaphone.
Super stiff RSB.