the n112 is part of the SAI, don't you trust me wilz??
Secondary Air Injection Solenoid Valve (N112) google it and prove me wrong!!
and if you search for this on here "Removing N249 valve -
How To Guide" then scroll down the first picture you see is of the SAI pump, and i think you'll find that the n112 valve is mentioned as being the SAI solenoid, so........................
if you have a search for that too rab it might clear up some questions you have about all these bits and pieces with funny names under the bonnet! or it might confuse you more!
and wilz tell andy where to shove his weekend working, nothing ever happens and its almost christmas tell him where to go!