OK, not sure about the legalities in asking this but does anyone have
(assuming it's legal to do so) a copy of that guitar riff that plays anytime
you buy a new part for your car in GT1?
I don't know exactly which one you mean but here is a link to a song from GT1, one of the related videos could be it. If you do find it on YouTube there is a less than legal way of downloading it, which I don't advocate by the way, but it may be your only option.
I'm going to have a quick look for the original disc so I can check to see if I can rip the soundtrack through the PS3, which is legal!
Update: I found the disc but after 12 years of ownership the game will not load, RIP Gran Turismo. I'm tempted to buy another copy from eBay, they only cost £2.29! I'm also trying to emulate the disc on the PC but so far no avail.
Another Update: Stupid me has realised that you want the jingle, I've managed to emulate the game and I am now trying to record the sound for you. I have also managed to record the sound but it's in not-so-good quality.