Drifting in GT4 is pretty tough to be honest. Out of all the Gran Turismos so far, GT4 is the worst for drifting because it seems just about any car which we can manage to get sideways could possibly suffer from
front-end snapback.
In other words, you get into the corner, get the rear loose (either thru throttle or natural lift-off oversteer) but when you try to countersteer in the opposite direction of the drift, the front-end all the sudden decides to grip more ferociously. So now the car is trying to go in the direction of the countersteer.
Things usually get ugly fast after this, and the entire car either goes into a spin, or you run out of track space trying to control things and now you're in the sand.
I went thru a period where I was trying different tire combinations, settings, and some other people's ideas here at GTP, but drifting in GT4 simply remained tough no matter what.

I was able to drift lots of cars in GT1, GT2, and GT3. GT4 like I said doesn't seem to work with the driver in this regard.
> To the OP: I would recommend any early Z cars: Datsun (excuse me NISSAN) 240Z, 280Z, and 280ZX.
> Infini III RX7s and AE86 Toyota Trueno/Corolla/Levins are also supposed to be good, but I haven't had that much success with these in GT4, although I have in earlier games.
> The older American muscle cars can also drift, although (trust me) it takes ALOT of concentration to get them sideways and keep them sideways without front-end snapback.