Mine first car was a Nissan Skyline (i don't know which one, i deleted my data about 50 times) My car right mow is a Toyota Supra 2.5GT Twin Turbo, tuned up to 426 hp.
My first car in GT4 was a 1991 Honda Civic. Not sure how much i tuned it up since this was back when i was starting my first playthrough 5-6 years ago.
I can't remember what it was on my best save (was only on 60%). My current save's first car was a Galant VR-4 *insert sappy flashback and "it seems like it was only yesterday" here*