You will need: A program called msceditor to modify your savegame's values.

https://www.nexusmods.com/mysummercar/mods/8

Install the file from this link and extract it to a folder of your choice.
AND
All upgrades to the car, this includes: Racing carburetors, steel headers, racing exhaust pipe, racing muffler
YOU DO NOT NEED NITROUS

1. Open Msceditor
It should look something like this.


2. Opening save game files in MscEditor
Click file.
Click open.
Click on defaultES2File.txt to select it.
Then click open.
It should look like this.


3. Inputing tuning values.
First lets tune the racing carburators.
Search for racingcarburators in Msceditor and input the number 17.1 into racingcarburatorsadjust1,2,3 and 4
ONCE YOU ENTER THE NUMBER IT AUTOMATICALLY CHANGES TO 17.1000003815
Then go to file and save you can save everytime you edit a value or at the end when everything is finished.

Tuning distributor
Search for distributor in MscEditor and input the number 15 into distributorsparkangle.
Then go to file and save you can save everytime you edit a value or at the end when everything is finished.

Tuning valves/rockers
Search for rockershaft in MscEditor and input the numer 7 into the outlined spaces.
Then go to file and save you can save everytime you edit a value or at the end when everything is finished.

1. Change spark plugs. Old spark plugs make a very big difference in performance.
in my case dyno testing the car with these tuning values and old spark plugs resulted in the car stalling and having a lot less power (163HP with old sparkplugs and 206HP with new sparkplugs)

2.Make sure you have enough oil and that its in good condition to prevent the engine from blowing up.

3.Make sure to fill up coolant so your engine wont overheat.

4.Before dyno-ing the engine heat it up to opeating temperature (middle of temperature gauge).

These values are meant purely for reaching max numbers and testing the limits of MSC. If you put 16.5 in the carburator tuning values you will get better drag times since the 17.1 tune gets a power spike at 7k-8.5k rpm which gets the engine to 206 hp. And the 16.5 tune has better power at 5k-8k rpm and a more even powerband therefore technically less power but better performance.


In short 16.5 = more even powerband and no powerspike and better performance
17.1 = max power but the actualy usable hp is only realy 150 (arround 5k-7k rpm where your engine usualy sits when driving)