Only if a X1 was in FM4... what? What are you talking about?
If you can't lap TGTT in less than a minute in GT5 with a X1 you, I'm sorry, can't drive.
I saw sub 35 times, not sure if sub 30 is possible (I've never driven the X1 on TGTT), but some dudes claim to have driven such times (although it's not necessarily the sort of people I'd trust ). But yeah, sub 35 is definitely possible.
Yes, it's indeed possible to go under 35 seconds in an X1. I've done it myself many months ago (sadly, I don't have any pictures to confirm it). - So, you don't even have to be an alien to do it .
Again, anything over 675PP should easily get around in under a minute.. I know my Audi R8 LMS Team PS is at 640PP and my 2J is at 660pp and I can get them both around Top Gear in under a minute (correctly).