Capacitors, in-line chokes and all the other tricks to improve interference!
Been there, T-shirt etc.
Finding the NGKs at a good price is pretty much essential, i tend to look on fleabay for sets of 6 for about a tenner delivered from carpartssaver/carparts4less/eurocarprats or go to my local parts factor and haggle for a deal on 12 or 18, depending how many i'm doing.
