I'm now pretty sure it was Knight Rider 2010.
the one scene I can recall involved the protagonist getting to choose between a beautiful red Lamborghini type car and a not-so-beautiful gray car.
There were actually a total of four cars. Three "beautiful" cars, with the second one being red. Then the not-so-beautiful car. It wasn't all-grey at first, but the next scene after it had been "chosen" showed it being extensively modded - after which it was.
he needed to go fast.
He did. To quote the script
Yeah, you're going after him,
this truck isn't fast enough.
The "truck" was the protagonist's monster truck - which now needed to be replaced with a fast car.
The first car was dismissed as too lightweight - the protagonist would not have been able to mount weapons on it.
What can I say?
A legend, creamy, runs like hell.
It's nice, but too light.
I put a machine gun on
there it's going to flip right over.
Then the red car - a FERRARI! The protagonist didn't want this one either, describing it as "temperamental" - and also quoting some stupid stereotypes about Italians.
Side note - this was not the red car from the previous film. According to Wikipedia, that had been a Dodge Stealth customised to look like a Pontiac Banshee IV.
Car number three, with the fins, is visible in the background. The protagonist ignored it in favour of seeing what was under that tarp.
The guy trying to give him the car had been egging him to choose the fancy red one because he knew it wasn't as good. It seemed like it was in a desert environment, and he needed to go fast.
Not quite. You can see from the photos it was in a desert environment, and the guy had made an effort to hard-sell the other cars. But the reason he didn't want to sell this one was that the engine was busted. However, the protagonist had a souped-up engine hidden away somewhere, and knew that since the car's original engine had been a V8, it wouldn't need that much modding to make room for the new one.
And, after a scene in which the car is modded, bulletproofed, and equipped with weaponry... here it is in all its grey ugliness: