Well, there is positively no good in tuners, only thief lack of speed makes up for handling.
My word of advice: choose an exotic or a muscle
To tell you, even though the muscle's handling sucks to the core, they actually pwn
The problem with someone when he uses a muscle is that he can control the car due to lack of sportsmanship. Here's a tip when you use a muscle, every time you turn sideways and jam on the brakes, the car slides, that will depend on your speed and angle during the turn
exotics: exotics are for the speed-demons like me
Exotics dominate by their top speed, which make a group of porsche carrera gt's invincible. I chose them because thief handling pumped to max is almost the same to a tuner and can keep a good speed. The time i defeated Wolf, Kenji Angie and Darius using Exotics, ONLY.
So........i'm not saying tuner is suckish, im just advising you to change your career.
I prefer Muscles but I don't seem to have any problems with Tuners. I like that you can tune them very nicely. I defeated half of Downtown (by default Bushido's territory) without any upgrades. After one of my last races I had to get some NOS. I upgraded it again before running against Kenji. After scoring his Pink Slip I am now on TFK (for the 5th time) with Kenji's RX-7.