1.2 exhaust emissions

[Leeboo]

I have a 12nv in my nova which failed mot on emissions output. The carbon emissions were nice and low but it was the hydrocarbons(?) which were too high. I had a 4 branch and ashley system from a gte on it, since mot I've fitted a full standard exhaust, is this likely to lower the emissions or will it need tuned?

[mowgli]

it will need tuning, and also take it for a good blast just before the retest