There's a hole in my airbox, dear Liza, dear Liza... (XJS)

[fizmo100]

Hi! While I was fitting new air filters to my 1990 XJR-s 6.0 I noticed the back of the driver's side airbox had an unplugged hole in it. I've included a photo showing that there's another hole next to it (to the left in the pic) which is blanked off. I'm wondering if anyone could enlighten me as to what should be in the open hole, is it normally blanked or is there a sensor missing? I'm wondering if that could be the purpose of the green connector tucked away to the left of the V12 badge? The car runs nicely, and has never given any trouble, but I'm concerned that the old girl could well have been breathing through the open hole in the back of the box rather than through the more resistant filter. Please also forgive the grubby state of the engine - it needs a good old clean this summer! Cheers, Dan.