Have recnetly fitted a Group A coil and Motorsport leads! Car runs like a dream now through the rev range, yet my idle is still all over the shop!

Sat at 1100 when I first started the car, after a few miles of driving was 900, then a few miles of hard driving it was about 500-600 for about 5 minutes until it went back to 900 but spluttering?
is there anything that cause cause such sporadic idling?

The car was R/R a week ago!