Hi, the one I use is only available in France it is a Dutch product I believe called Tecflow speed cleaner, I cured main cold start problems with it (when it was due to bad atomization).
I don't know which product you have available in the UK, I left too loo ago. Other members will be better advice on this, but as preventive treatment I use "Liquid Engineering Fuel set one" just "Google it" I get it from the UK, and use a dose per tank, (1L:4000L) I slighlty overdose it. But in 200 000Km with my Lancia Lybra 2.4 not a peep out of the EGR. Only 30 000 on the Alfa 159 ti 2.4, might be too early to tell.
Any way to put cleaner in, wait until your tank has gone done more then put it in then put more a little more fuel in it to mix well.
If it only happened after this load of fuel then a Cetane booster should do the trick ie. WYNNS. Or Kerosene if you have some. (just can, but just joking).