I think it's more likely the GTX3 is inherently screwy with the throttle/steering that you are used to, than something wrong with the 3PV. The GTX3 is almost identical to the Flysky GT3B.

While I haven't driven much with the GT3B, the Flysky GT3C definitely has some weird transmitter behavior -- the steering has a bunch of added expo, I had to drop -30 to -35% on the expo to get it to drive linearly.

On the throttle front, the GT3C has some kind of throttle easing when going from throttle to neutral that keeps the car flatter in the air. I tested a Sanwa MX-V, Flysky GT3C, and Futaba 3PV back to back to back in the exact same car. While the Sanwa and Futaba behave simiarly, it was clear the GT3C has some abnormal steering and throttle behavior. It's also not linear like most transmitters, I had to dial in 10-20% of throttle expo (I can't remember what we ended up with) to get it to behave correctly.

Check out my blog for more info on the differences.

http://razorrc.tumblr.com/archive