Didn't read through all the pages of this thread but here are my mine, simple but effective:
"That exhaust really come out the side like that?" - Nope, I'm just a huge poser.
"How fast ya had 'er up to?" - 65, I have never broken the speed limit, ever.
"What ya got done to 'er?" - I hope you packed a lunch, I need a few hours to answer that. Instead, maybe you can just look at the car and investigate.
Back when it had the stock rear bumper/hood:
"Ya know you gots the wrong bumper on the back right? Suppos'ta say COBRA"
"Why's it got that GT hood on there?"
Also, not really questions, but:
"LITE EM UP!!!! YEEE HAWWWW!!!!" - Comin right up buddy!! Tires for 19's are cheap.