I found it the other way round.
James May getting lost was amusing, Clarkson shouting "Poooooowwwwah" in the Porsche got a giggle, but the rest of it was a bit meh. It was obvious that the lack of trousers was staged, but seeing him waddling around in black gaffa tape was better than the "we accidentally forgot about picking the bride and groom back up" bit.
the thing you've got to bear in mind with "challenges" like that is that its essentially a soap opera / planned storyline. just because its obvious whats going to happen doesnt mean it cant be funny.