MOT Emissions

Dear All,

I bought a 993cc hijet bus. It had no MOT and I suspected that the head gasket had gone. Paid what I hoped was a bargin price.
Well a lot of testing and head scratching later, the head is ok and it failed MOT on emissions.
It has been messed with.
It is running rich hence the MOT fail on emissions.
Firstly all the little tubes were in the wrong places.
I have serviced it which made a difference.
Changed the Lambda sensor.
Tested the MAP sensor, sucking on the pipe watching the voltage fall.
The throttle position sensor seems to work. Make on tick over and the other contacts make on full throttle.
I have changed the water temp sensor for the ECU as the temp sensor for the dash was under reading.
New dizzy cap, rotor, plugs and leads.
This thingy (technical term)

Had the pipe connector missing and the hole bunged up. There appears to be nothing inside it, like a diaphram, so I drilled a hole in the end and slid over a piece of silicon tube. As the engine warms up it now surges on tick over.

Any thoughts would be grateful.