The bottom line is, whatever magic aero Lambo has done seems to work. I was told by the Lambo rep that the Performante repeatedly did 6:53 lap times on the ring just before nabbing the 6:52 time. Lambo had debated on just using the 6:53 time since it was consistent, but then decided that records are records and don't need to be averaged. He also said the SV actually did one high 6:57 time but Lambo felt it was not the official time since it was never repeated.

This is not just a wing and call it a day. The air actually gets diverted by the winglets and send it up through the wing channel and out through the smooth hollow wing (which is why forged carbon had to be used, smooth inside as well as outside). No one has ever attempted such a feat in a production car before. If you look at the back side, the entire rear bumper is a downforce wing. A motor in the front air dam also moves a flap (I was told this all occurs in milliseconds). A lot more than just the rear wing are at work here. I think from a technological aero standpoint, Lambo has placed itself ahead of the game. I give credit where it is due.

The lambo rep said that during cornering, yes. In a straight line at certain speeds, he said the downforce is reduced 20% over the standard Huracan. Here's how he explained it... He said that by default, in the closed position, the winglets do nothing and the wing produces up to 750% more downforce in the rear than a Huracan. But when going in a straight line the winglets fully open and divert air away from and reduce hitting the exterior upper side of the wing. The way they do it is by diverting the air through a channel under and inside the wing. This actually creates lift with minimal drag and lightens the car. The net effect in the straights is minus 20% downforce over not having any aero at all. He said that even on the road this will be noticable. He claims the rear end will feel lighter and more playful than the Huracan when you want it to be, yet it will stick like glue in the corners when in track mode.

Well, since they didn't give a number, here's how we can calculate it based on some current facts.

The last LP570-4 Superleggera produced 110lbs of rear downforce at it's top speed of 202 mph.
The LP570-4 SuperLeggera produces 50% more downforce than the standard Gallardo.
The Huracan produces 50% more downforce than the standard Gallardo using underside aero.

So the Huracan produces around 110lbs of rear DF at 202mph.
750% of 110 is 825 and 750% more is 825+110 = 935lbs of DF at 202mph.
I don't know what this translates to at slower speeds, that's where the aero experts come in.