i cant speak for the iridium plugs , but i do know about the ngk's. there is nothing else to run in a mitsu vehicle. ive tried all the others, ive been an autolite fan for years and they wont run worth a crap for more than like 1 month at best. ever since i learned this i went to ngk's and havent had a minutes trouble yet. ive tried the platinum ngk and have found almost the identical results from the standard ngk. so i say why spend more money if you cant see any improvements. this isnt just in one motor, ive owned over 20 mitsu trucks and i have 4 at the moment including a mits. starion with turbo and lots of fuel being dumped thru it. the standard ngks work better in it than the platinums. may not be the case for everyone but i wont run any other plug.