Emissions MOT fail S2 Colone 2.9 injection

[LenChim]

Ok, so it failed, changed the plugs as they were looking a bit variable in color set at 0.7mm, new HT leads, the old ones had seriously odd resistance (ohms) readings, cleaned the thermisters in the air flow meters. Cleaned the air filter. Checked the ignition timing, and there seems to be a lot of variation in what is correct for the timing so set it at 12 deg before TDC at tick-over. Any better suggestions? Does it affect the emissions that much?
I think that I could take out the fuel injectors and clean them and make sure that they are giving a decent spray and cut-off.
Is there anything else that you can suggest that may help?