It goes to around 603/604 in certain combinations with stock parts but switching those out for racing parts drops it to around 593-599. I have not tried all combinations yet and this was what I found with my initial playing.
Extras:
18" rims with wide tires/wide offset
Weight reduction stage 1, 2, 3
Racing Soft
Bore Up
High Left Cam Shaft
High Compression Pistons
Racing Crank Shaft
Fully Customizable computer
Medium-RPM Turbocharger
Fully Customizable LSD
Increase Body Rigidity
Stoke Up
Engine Balance Tuning
Polish Parts
Racing Intercooler
Racing Air Filter
Racing Muffler
Racing Pads
View attachment 1233840
I have not played with the gearbox yet beyond adjusting the top speed.
View attachment 1233841
I was unable to add the Racing Brake Kit as that pushed it over 600 and I had tried with others yet and I needed a max 600 tune.
Change any of the Intake & Exhaust or remove the Racing Intercooler and the PP increases (601 - 605). For example:
View attachment 1233845
View attachment 1233849
I might play with other add ons to see what happens as I love this monstrosity however the challenge I have is in the suspension and LSD tune. Currently this is fairly neutral (compared to what I started with) but there is still a tendency on certain cambers or corners for the rear end to want over power the front and drive you into a barrier. That said, its a pretty competent Suzuka car now for it's PP rating.
EDIT:
I just tried a max build testing the low and high RPM turbochargers with the Racing Brake Kit.
Low-RPM
PP 626.98 - 250HP, 234.6 ft-lb
Medium-RPM
PP 635.36 - 263HP, 237.5 ft-lb
High-RPM
PP 629.60 - 272HP, 236.3 ft-lb
What is interesting though is if you drop the brakes to normal (with racing pads) then the low and high RPM stay above 600PP but the medium (as above) drops below 600..
I just found another massive glitch!
If you add the sports brake kit, then with the low-RPM turbocharger the PP drops to below 500!
View attachment 1233861
This does not work with the other turbochargers which remain above 600...
EDIT: I just found the new tune a few posts up. I added the suspensions and LSD updates to mine which improved the rotational G for 150 mph. Thank you. What I found is if you select the low-rpm with my component selection the 150 mph stays in the 0.22 value and PP is at 459.92. As soon as you select one of the other turbochargers then the rotational G jumps to 1.6 and the PP 600+ respectively. Must be a glitch but I have not tried to drive this yet.