If you turn both idle screws clockwise a quarter of a turn at a time until you are happy then don't worry, you shouldn't disturb anything else. Equally if you want to slow it back down a touch, turn both screws anticlockwise 1/4 of a turn at a time. The idle screws on mine are conveniently cross-marked. Give it a few revs between each adjustment and let it settle... patience required!
I agree tappets.
I learnt something at the Twiddle day about this. Pete (the guru) showed how you can actually adjust the tappets while the rocker cover is off and the engine is running! Mine were all well adjusted, but I still had a tappet noise. Pete on the day went though each valve sliding a thin feeler gauge under each tappet until suddenly there was peace! Engine stopped, that particular tappet was tightened and hey ho sorted. Very little noise at all from my 6 pot - it just purrs.