I have gotten both the Toyota Supra and the Zonda down in under 7 seconds.
All with level 3 parts. First of all you will need to adjust a few settings.
Start off with the engine, follow my other hint to push your car up 100hp.
Then make the rear wheels with as much tread as possible with a large profile and hard suspension. Then drop the pressure below half way,(actually done with real race cars) now make the front tyres considerably smaller with a softer suspension so you can absorb the launch start, then change the direction of the front tyres to point inwards so it is harder to turn but better for the drag strip. Now gears are tricky, you want the gears sorted in an asending order with the 6th gear being the highest. You also what the drag spoiler fully extended. Adjust the NOS setting to be more explosive than lasting

As for the actual drag race you want to hit perfect launches all the way down, easier said than done but to beat 7 seconds you need to.
Around 2nd and 3rd gear hit NOS and that should take you through to 5th gear. The hard part is keeping your car in a straight line when you come down from the launch, which I have no real advice for.

Then pick your favourite track and your favourite side, as it does make a difference, and max out the burn out and then try and try.

I use this for drag settings, it may cause different effects in other styles. In the tune section for your car go to the engine part and then push the cam all the way up to advanced and then push the start and end boost all the way up. This will give you better performance and top end RPMs, it should also push up your horsepower by atleast 100. If it doesn't then upgrade all performance parts to level 3.

Firstly I’m not sure if the tokens you pick after winning or dominating a race day are randomly generated. After I dominated the first race day into beating the Speed King I picked the middle token, which gave me a Free Car Marker. Which I obviously used on a Zonda, which I used to beat the Speed King, as you need it to beat the other Zonda’s you race. Another hint is to max out on repair and total repair markers as you may need them.

To do a winning wheelie first you need a rear wheel drive car. Then upgrade the performance to around level 3, until it has above 400-500 horsepower. Then once on the start line hit perfect launch and try and hit perfect launch all the way up to third. Once you start to see the bonnet falling hit NOS and this should push the nose back up. This is the method I use and I have maxed my Chev SS to 1343 feet. Good luck.