Found this plug under the bonnet

Down behind the dipstick/oil filter. What is it, what is it for, why is there nowhere for it to plug on to ?

int that the doors fallen orft detecter or summit ?

can't be that, it dun't get wet !

Think it's from the MAP sensor OP, have you had the inlet manifold off sometime and forgot to replace the connector?

thought that was at the back of the engine, next to the air filter ? or is that the maf sensor ?

Inlet manifold was off over a year ago (by garage) when I had injector troubles, can't say whether it was like it before it went in or not. Surely, I would have noticed some ill effect if it's been off all this time ? I doesn't seem long enough to reach anywhere to plug in.

just found a picture from when I changed the intercooler hose, and it wasn't visible then, so hopefully I can put it to bed, now I know it could be off the inlet manifold, thanks to chaser.

Yes it's the MAF thats at the back.

Have a look at the inlet manifold, opposite end to the EGR, low down there is a small flattish square shaped sensor fixed with a single bolt to the end of the manifold. The connection pushes upwards to the bottom of it. (hope this is making sense)

H'mm seem to remember unplugging that when I did my inlet manifold clean (oven cleaner style).
Does it run ok with it off? Should it?

If it's left off the ECU uses a default pressure reading so engine will run ok.

10/10 Chaser, found it and plugged it back on no problem. looks like it's been off for ages, I've never had need to disconnect it, so it can only have been down to garage.

Although engine has been running okay without it, I felt that the performance wasn't what it should have been, which led me to clean the EGR valve. However, on the drive home from work this afternoon, having reconnected the MAP, thanks to Chasers help, it did seem to be back to what it was as I remember when I bought it. So although it runs without it, I think it runs better with it.

Thanks again Chaser.