Two types of booster have conclusively been shown on here by the most experienced mappers to give gains in octane (less knock). Both NF and Lucas are the recommended products and are available from some of our site traders.
Now without knowing what car Dave is driving or if its been remapped & for what type of fuel I wouldn't dream of giving the above advice
I got mapped by Simon for E5 on its own, when we got back i added around 140mls of NF and topped up with E5 for the second map, all fuel was from the same service station, i think Simon said that he could advance the timing by 6 or 7 deg.
Any of the top mappers will tell you what a difference good octane booster makes... Bob Rawle told me not to go above 0.5bar without the NF mixed in as the timing was so much more advanced with the NF added..
There are some octane boosters that are useless but NF race formula and Lucas octane booster are proven to enhance performance.
Dublin southside would be Ciaran in ASD, based near walkinstown roundabout. Sells NF at a very good price