My last car was a 2000 Civic that wasn't winning any drag races, but handled like a slot car, and the 335 is currently a step in the complete opposite direction. I've focused more on engine mods so far, so it's a rocket in the straights, but still needs some work for the twisties.

Cosmetic

OEM BMW Gloss Black Grilles

Black Painted Lower Grilles

Sapphire Black Reflectors

WINCOS HCD-20 & HCD-30 Tint

BMS Amber Angel Eyes

TWNTRBO Vanity Plate

Engine & Drivetrain

RB Turbos w/ N20 (3.5 bar) TMAP Sensor

93 Octane Protune by Cobb Plano

xHP Stage 3 TCU Flash

DEFIV Differential Lock-Down

BMS Dual Cone Intake

STETT Charge Pipe

Forge 007 Diverter Valves

Helix Front Mount Intercooler

CP-E Catted Downpipes

Walbro 450 Low Pressure Fuel Pump from SteveAZ

RB PCV Valve

Suspension/Brakes

Bilstein B12 Pro-Kit

OEM BMW M3 Control Arms

OEM BMW Pads/Rotors

Rims/Tires

18x8.5" Black BBS CH - Front

18x10" Black BBS CH - Rear

225/40/18 Michelin PS A/S 3+ - Front

265/35/18 Michelin PS A/S 3+ - Rear

Audio

Stock Logic 7

JL Audio XD600/1 Sub Amp

Musicar Northwest E92 Sub Enclosure with 12" Morel Ultimo SC sub

My 335 as I bought it in 2010.		And more recently, after some modding.
Dyno from Cobb Plano's Mustang Dyno.		And in Excel, looking at gains.