By now, you're likely already at 400-500hp but there are some things you should still note about upgrading your car.

There's two key stats that you seriously need to watch out for when upgrading your car:

• Engine strength
  
• Cooling

Engine strength, basically is how much stress your engine can handle.

E.X when you have a high power NOS but a weak engine, your engine is more prone to blowing up.

You can get this stat up by buying:

• Prototype/Circuit Engine headers
  
• Prototype/Circuit Engine block
  
• Protoype/Circuit Pistons
  
• Protoype/Circuit Cylinder heads
  
• Prototype/Circuit Spark plugs

Cooling, is pretty much self-explanatory. It's how much your car is able to cool down the engine and it's fluids.

You can get this stat up by buying:

• Prototype/Circuit Intercooler
  
• Prototype/Circuit Radiator
  
• Prototype/Oil cooler

If this stat gets to low, your engine is at a higher risk of overheating, resulting in a highly noticeable decline in performance.

You can get this stat up by upgrading your radiator, intercooler, oil cooling, etc.

By now, you've likely paid off your debt and probably have/haven't taken out a second or so loans out from daddy Yazuka.

You should be careful with this, I should've mentioned this in my previous guide but if you fail to pay off your debt (you waste your entire betting loan, and make nothing in return to go towards your debt), daddy Yazuka will take the car you're currently driving away from you.

How do you avoid this?

It's simple, stick to racers you know for a fact you can beat.

Considering you've made it this far into the game without this happening, you likely have a lot of cash leftover from racing. Now would be a good time to start buying multiple cars to prevent the death of your player save.

Now, overtime through tons of racing you might've racked up a ton of rep.
Once you have enough rep, you get to challenge the bosses of Tatsumi PA.

The four bosses currently are:

G-Company
• S.K - Unlocks at 5k rep
  
• Star Tamer - Unlocks at 10k rep
  Endless Appeal
  
• Sonny
  
• Eternal son

Boss races work similarly to drag races, there's multiple rounds in one race.
Unlike drag races, it isn't best out of 3, it's best out of 5. Meaning you have to win 3 times in order to successfully beat the boss.

Now about the bosses you'll be taking on,

S.K, is fairly easy and you likely won't struggle with him too much if you already have a powerful car, so I won't be talking about him too much. S.K also makes fairly sized wagers.

S.K uses a Sannis Livisa 180RS (or 200RS), meaning if you built your car up properly you should have little to no issue.


On the other hand, Star Tamer is quite a handful. Unlike us, he uses a GTST, the GTR's RWD sibling.

Star Tamer is by far one of the fastest racers on the Tatsumi PA, and will definitely ram you around.
Star Tamer makes a very big wager, of 4.7 million yen. One slip up, and it'll likely cost you the race and a TON of money if you lose.

Star Tamer is definitely possible to beat, just don't expect to absolutely walk him like all the other drivers.

Same applies to both Sonny (rep boss) and Eternal Sun (Crew boss).