First of all, I'm not an artist, I consider myself a diligent hack, so keep that in mind.
I agree the font didn't match up. I'd go with either a script type font or a copy of the font the car maker uses. Is that a Lambourghini?
Anyway whatever it is, it looks like it dripped off the assembly line, so make the font kinda wet looking.
I had a hard time making out the outline of the car, so I glowed it, probably too much, but you get the idea.
Lastly, if you want to make the GBATMW a watermark, kinda blend it in with the starburst.
Speaking of the starburst, I think it looks really nice, I'd keep it, and I'd like to know how you did it
Here's a rough example of what I'm talking about, forgive the mess.
I think you did a great job, and could keep the sig exactly how it is, but you wanted comments, so I hope this at least gives you an idea or two.