I got the Corvette ZR1 with the CAU crates. I got the Perf spec first, because I'm broke and couldn't afford the Circuit. It's a really good car, only around level 800 though. I upgraded it up and over the level of my Perf BMW. I got the Circuit spec soon after and immediately fell in love. It's quite fast and has really good steering, even at high speeds, I also pulled off a thread the needle in it. I'll edit this to post a link to the video when I post it on Youtube. I'm working on upgrading it but I don't expect to easily get it better than my Camaro or GT.
I played a lot of CAU crates, most of them being I was invited to it as a protector of the transporter. Protecting transporters when they're in Perf cars is hard because the exotic supercars are too overpowered, I have to use my GT going 260-280 MP/H to keep up with them. Another thing that bothers me are the guardrails. Guardrails are useful when you're on the road, because you can use it to help steer, but when you're on the outside they are a pain. Especially in an Off-Road CAU chase and you hit a guardrail from the outside and it stops you.
For once in my life I met someone ingame who was lower level than me. Everyone I come along to in Free Roam is always overpowered compared to me, but I saw two players who I got to help with some of the first missions, which leads me to talk about Specs. I hate Street spec, my highest leveled street car is level 782. I used to be really serious about street specs but I don't like it as much anymore. I feel the same for Dirt, I have a low-ish leveled Raptor that I use for Dirt races and I just cannot steer in it. I get 4th or 5th every PvP race in dirt spec. I'm pretty cool with Performance, I have that Corvette that works like a charm, but all those exotic supercars are very overpowered for Perf spec. Raid and Circuit are my strongsuits, I've always done pretty well in Circuit races, especially on actual tracks rather than dirt roads like that Hill Climb race. Raid is my best spec, I've even had people blaming me for hacking when I win raid races by 10-20 seconds. I don't hack, I'm just good at it.