None are made for our cars as far as I know. But there's no need for aftermarket rails either. You'd probably need to make 400+ HP before they'd be necessary.
On the other hand, 5th gens use a different fuel rail setup than the 4th gens. A separate feed to each fuel rail, with a regulator at the end of each fuel rail. Should maintain pressure/fuel better at the rear cylinder bank, and would be a good idea on 4th gens. I think it would clear up some of the rough power delivery (jerky acceleration, hesitation) that I and other modified 4th gen owners experience.
On the other hand, 5th gens use a different fuel rail setup than the 4th gens. A separate feed to each fuel rail, with a regulator at the end of each fuel rail. Should maintain pressure/fuel better at the rear cylinder bank, and would be a good idea on 4th gens. I think it would clear up some of the rough power delivery (jerky acceleration, hesitation) that I and other modified 4th gen owners experience.