I have had the MkIV for a few weeks but never drove it. They are money sinks once you reach $20 mil.
I had a few goes on various tracks and I gotta say... I kinda dont like it.
Mine has no weight loss but 630hp + HSG tune + 5 spd box with 330km/h final drive.
I can see why its good around Le Mans... I can actually cruise and get good times... its consistent and you "get" quickly how the car drives.
But its not so good on other tracks.
I mean these are Le mans cars... they may not do well on say Interlagos.
IMO you should have the 330, Mk4 and XJ13, they are the $60 mil. crown jewels but the 330 kills everyone anyway any track any weather. I think a *stock* no upgrade 330 p4 is faster easier to drive and more consistent than the other two with upgrades.