Lots of questions

I am new here and it seems you guys really have the Foremans figured out so here it goes: My silencer turned purple, this was after alot of road riding after 30 break-in miles, it now has 103 miles. Did I hurt it by running it fast that soon. The book said 15 miles initial break-in. We were going 40-50 mph for some time Next, what is the deal with everyone switching to NGK iridium plugs? Are there any benefits? What is the vent hose relocation about? Basiclly, what cheap little mods can I do and what do I look out for or watch closely on these? Seems like a great quad, and the power steering is REAL nice! Thanks for the help!