Different engines seem to get on better with different plugs, i obvioulsy cant comment on why you were told by stu not to run them on your motor but ive had great success with iridium plugs on nitrous, in fact on my 2.0 16v vauxhall motor ive run increases of 100% power using nitrous on iridium plugs and its never missed a beat and still idled perfectly, never needed a plug change in 18 months use like that and they were still working perfectly.

But different people always seem to have their favourites with plugs, a bit like how some people always prefer spax to koni or vice versa just cause its what has worked for them.

hopefully Stu can give some input as to why he doesnt like the iridium plugs??