The Karin Previon from the Los Santos Tuners update with ALL tuning parts included and fully usable, along with a moving & tunable steering wheel and all liveries.
I've included the .max project file for anyone who wants to make their own fully tunable car.

The car is FULLY stable with 208 tuning parts, it can be shot, spawned 10+ times, thrown into dynamic objects or exploded without the game crashing.

REQUIRES v21.09.26.1 or newer of Zolika1351's Trainer/Mod Menu to work, otherwise the car is completely unusable. To be able to purchase tuning parts in Pay 'n' Sprays, navigate to Vehicle Options and enable Pay 'n' Spray Mod Garages
PUT PREVION.DAT INTO THE "carmods" FOLDER! (if it doesn't exist, create a folder called "carmods" in your game folder and put the .dat there)

Use https://gtaforums.com/topic/955449-iv-zolikapatch/ to make the steering wheel move and the engine shake

Note that because of the high amount of tuning parts, this car might cause performance issues on low-end systems.

Vehicles.ide:
previon, previon, car, VIGERO, SABRE, VEH@LOW, NULL, 1, 0, 0.2004, 0.2004, 0.5 4, 1.0 ,1, livery+wheelangle:-18.343
txdp
vehshareV, vehshare
race_interior, vehshareV
race_generic, race_interior
previon, race_generic

Carcols.dat (car4):
previon, 74,0,83,90, 0,1,1,133, 3,1,1,133, 10,1,1,133 25,1,1,133, 37,1,1,133, 53,6,1,133, 61,1,1,133, 75,1,1,133, 92,1,1,133, 6,0,12,133, 10,0,12,133, 21,0,12,133, 23,0,12,133, 25,0,12,133, 33,0,35,133, 34,0,34,133, 47,0,35,133, 49,0,63,133, 52,0,56,133, 54,0,55,133, 65,0,63,133, 67,0,118,133, 70,0,65,133, 98,0,90,133, 16,0,76,133, 9,0,91,133, 15,0,93,133, 19,0,93,133, 13,0,80,133,

Tuning part count: 208
Tuning part list:
Polished Strut Brace
Carbon Strut Brace
Medium Polished Strut Brace
Polished Tri Strut Brace
Carbon Tri Strut Brace
Primary Tri Strut Brace
Secondary Tri Strut Brace
Arc Strut Brace
Secondary Arc Strut Brace
Tower Strut Brace
Secondary Tower Strut Brace
XL Tower Strut Brace
Secondary XL Tower Strut Brace
Titanium Strut Brace
Polished Twin Bar Strut Brace
Extreme Billet Strut Brace
Racer Strut Brace
Carbon Racer Strut Brace
Primary Racer Strut Brace
Secondary Racer Strut Brace
Sports Seats
Painted Sports Seats
Carbon Sports Seats
Ballistic Fiber Sports Seats
Painted Tuner Seats
Carbon Tuner Seats
Ballistic Fiber Bucket Seats
Painted Bucket Seats
Carbon Bucket Seats
Ballistic Fiber Bucket Seats
Painted Track Seats
Carbon Track Seats
Ballistic Fiber Track Seats
Carbon Race Seats
Custom Front Bumper
Street Front Bumper
Race Front Bumper
Drift Set Up Front Bumper
Street Half Cage
Dash Dodger Cage
Padded Dash Dodger Cage
Full Roll Cage
Padded Full Roll Cage
Chrome Plated Rail Covers
Primary Plated Rail Covers
Secondary Plated Rail Covers
Chrome Meshed Rail Covers
Primary Meshed Rail Covers
Secondary Meshed Rail
Chrome Smooth Rail Covers
Primary Smooth Rail Covers
Secondary Smooth Rail Covers
Chrome Bolted Rail Covers
Brushed Full Rail Covers
Primary Full Rail Covers
Secondary Full Rail Covers
Primary APX Rail Covers
Carbon APX Rail Covers
Brushed APX Rail Covers
Primary GT Rail Covers
Secondary GT Rail Covers
Super GT Rail Covers
APX GT Rail Covers
Brushed GT APX Covers
Alloy GT APX Covers
Brushed GT APX Covers
Racer GT Covers
Tuner APX Covers
Full Colored Interior
Semi Stripped Interior
Race Dash & Stripped interior
Carbon Dash & Stripped Interior
Single Tacho
Dash Gauges
Pod Tacho & Dash Gauges
Pod Mounted Tacho
Rear Diffuser
Primary Tipped Diffuser
Primary V8 Engine
Primary Ridged V8 Engine
Secondary V8 Engine
Secondary Ridged V8 Engine
Square Exit Exhausts
Dual Exhaust
Dual Titanium Tipped Exhaust
Titanium Tipped Exhausts
Street Exhaust
Angled Blast Pipes
Straight Blast Pipes
Primary Bolted Front Fenders
Primary Front Fenders
Primary Rear Fenders
Primary Bolted Rear Fenders
Green Light Glass
Red Light Glass
Blue Light Glass
Yellow Light Glass
Neo Light Glass
Side Vented Hood
Carbon Side Vented Hood
Vented Hood
Carbon Vented Hood
Street Hood
Carbon Street Hood
Fully Vented Street Hood
Carbon Fully Vented Street Hood
Tuner Hood
Carbon Tuner Hood
Carbon Hood
See-Through Hood
Chrome Hood Catches
Angled Hood Pins
Latch Hood Pins
Blue Latch Hood Pins
Red Latch Hood Pins
Gold Latch Hood Pins
Plastic Upper Intake Manifold
Plastic 450CUI Intake Manifold
Prim. 450CUI Intake Manifold
Sec. 450CUI Intake Manifold
Brushed V8 4 CAM Manifold
Brushed V8 Air Intake System
Primary V8 Air Intake System
Secondary V8 Air Intake System
Plastic V8 Air Intake System
Custom Intercooler
Intercooler w/ Water Sprayer
Small Logo Intercooler
Large Logo Intercooler
Intercooler w/ Twin Fans
Street Roof Scoop
Tuner Roof Scoop
APX Charger
GT Charger
Dinka Charger
Street Skirts
Tuner Skirts
Race Skirts
Custom Skirts
Street Race Setup Skirts
Plastic Splitter
Secondary Splitter
Primary Splitter
Carbon Street Splitter
Primary Tipped Canards
Carbon Race Splitter
Race w/ Primary Canards
Race w/ Secondary Canards
Secondary Tipped Canards
Apex Basic
Sprint MK II
Sprint Lightweight
Sprint Featherweight
Sprint Professional
Rally Basic
Rally Clubman
Rally Professional
Formula Cutout
Sprint Premium
Sprint Redmark
Sprint Ultimate
Rally Advanced
Formula Professional
Sprint Basic
Sprint Clubman
Primary Sunstrips
Plastic Sunstrips
White Fukaru Sunstrip
Black Fukaru Sunstrip
White Meinmacht Sunstrip
Black Meinmacht Sunstrip
White Powermetal Sunstrip
Black Powermetal Sunstrip
Custom Spoiler
Apex Spoiler
Small Spoiler
Race Spoiler
Tuner Spoiler
Street Spoiler
Competition Spoiler
Big Wing
Stacked Spoiler
Chassis Mounted Spoiler
Chassis Mounted Spoiler Alt