Can You Beat Gran Turismo 4 Without Upgrading Any Cars?

Can you, or in this instance I beat gran turismo 4 without upgrading a single car? Well this challenge won't be easy, but let's do it!
   • Gran Turismo 4  

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Specs/Sens/Peripherals

Same sens for all CoDs BO4 onwards: 1800 DPI | 4.8 sens relative | 1.78 coefficient | Default windows sensitivity

Graphics preference: Typically all lowest in every multiplayer game.

Gaming PC
CPU: Intel Core i9 11900K
GPU: EVGA NVIDIA GeForce RTX 3080 Ti
RAM: 32GB (2x16) G.SKILL 32GB Trident Z NEO RGB DDR4 3800MHz
PSU: Corsair RM750x - 80PLUS GOLD
Cooling: Corsair Hydro H150i RGB PRO XT 360mm AIO
MOBO: ASUS ROG STRIX Z590-F GAMING WIFI

Other
Keyboard: Logitech G512 (Looking for an upgrade)
Mouse: G502 Lightspeed (Not the newest one)
Gaming Monitor: HP Omen 240hz 1440p
Mousepad: SkyPAD 3.0
Headphones: Audio Technica ATH-M50x
Microphone: Blue Yeti
Capturecard: Elgato HD60

0:00 Introduction/Explanation#
2:02 Sunday Cup
3:23 FF Challenge
7:40 FR Challenge
10:29 4WD Challenge
11:29 MR Challenge
17:20 K Cup
19:18 Spider/Roadster
22:29 Truck Simulator
27:08 Clubman Cup
32:27 Tuned Car Cup
39:56 NA Cup
42:18 Turbo Cup
43:08 Boxer Spirit (Very Hard)
47:00 Boxer Race 2 (EXTREMELY HARD)
52:25 World Classics
55:55 Tokyo Drift
56:40 Compact Car Cup
59:40 Supercar Cup
1:07:45 GTWC Planning
1:08:52 Nostalgic Rally Moments
1:12:00 GTWC Begins
1:12:32 Race 1
1:14:45 Race 2
1:18:50 Race 3
1:25:00 Race 4
1:27:25 Race 5
1:29:00 Race 6
1:33:26 Race 7
1:36:50 Race 8
1:41:20 Race 9
1:43:17 Race 10
1:49:25 Results
1:51:05 Bottom Gear?