trunk liner and mats: either from the OEM or weathertech...check the for sale listings and you might find one cheap.
coding: little things like autofolding mirrors when you lock, enable remote closing rear hatch, enable sport displays, etc
grill: check for sale...are you looking for all black or? I like the m-style double fin grills myself, just wish they were available for pre-LCI
check out alternatives to JB4...some places offer actual tunes, or another piggyback tuner similar to JB4 that I like is racechip ultimate
https://www.racechip.us/shop/bmw/x3-...-255lb-ft.html
Improve throttle...either what racechip offers or sprintbooster
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Current: 2020 X5 x40i M-Sport, Arctic Grey Metallic / Ivory White, Executive Package, Luggage Compartment Package, Integral Active Steering, Tow Package, Parking Assist Package, Driving Assist Package, M-Sport brakes, Tux Mats