So aside from the previously mentioned special parts these WP cars have, some of them appear to be amped up beyond what the standard versions are capable off, like the PO cars for example.
The normal Ford GT has a max PI of around 987 with awd, 910hp max and weighs under 2500lbs with rwd.
The WP GT starts at 998, factory rims are as light as the lightest rims, has 1078hp max and can weigh well under 2400lbs(2,368 with aero) and is capable of 3Gs in handling with aero.
The normal Porsche 718 has a handling stat of 9.4 in a S1 handling build, The WP 718 is capable of 9.9 with the exact same build, but the extra grip means less power to put into it to keep it S1.
The standard Jeep CJ5 with a fully built stock engine(turbo’d), all possible weight shedding and biggest off-road tyres equipped has 389hp, weighs 1,756lbs and has a 6.3 handling stat with no aero and 794PI.
The WP CJ5 standard engine is more powerful than the standard CJ5 WITHOUT even bolting on the turbos at 462hp N/A and over 600hp with Turbos.
While heavier at 1,936lbs stripped out, the WP CJ5 has a 7.2 handling with no aero and 825PI.
No obvious differences on the Subaru Rally car, (aside from the pre tuned part.
) stock engines on both make the same power and torque.
The WP Gymkhana 9 Focus is slightly different as it starts at S1 900 which isn’t feasible for the normal one with the stock engine.
The WP Toyota T100‘s stock engine has a slightly higher engine sound compared to the normal one, plus a small power hike to 793hp fully tuned compared to 758hp of the normal one.
The WP Aventador has a slight grip advantage at 8.4 to 8.2 on a normal Aventador with race tyres equipped, the Liberty Walk wing is adjustable on the WP and not on the normal one.
The WP F50 GT has no major differences aside from starting PI and the tyre difference that was listed by
@WanganDream in his post. 👍
So some cars have major improvements, some minor and some with no extras added.
Small update: The WP F50GT does have a major difference, The engine sound is identical to the LaFerrari’s.