I bought my ITR straight from japan back in febuary this year and when i got it i done the usual things, oil/filter/timing belt etc. I also checked the spark plugs and found they were HKS iridiums (S40i) They were a good colour (light tan/brown) and there was no staining on the ceramic part so I figured they'd do ok for another while and put them back in again. Then tonite i decided to have a look at them and when i pulled the first one out i discovered that they only had a 0.03" gap (0.8mm) whereas the stock gap for the ITR is 1.1mm. The car drove 100% and pulled very strong through out the rev range with these plugs in, i got good gas mileage when i wanted (36mpg on long journeys) and there was no missing or pinking etc. Anywho i put in a set of denso iridiums (heat range 6 and gapped to 1.1mm) that i had lying about, theyre not new but i figured they do till i got a set of NGK platinums...i havent noticed any difference, the car still drives/pulls as strong as it did before etc etc so how was the car able to run so well with the incorrect gap (it was off by over 25%) and to run this gap plug would the previous owner have retarded/advanced the timing any (havent got a timing light to check it) Could the wrong gap plugs have caused any problems/damage

 

Just found out that the S40i HKS plug has a heat range of 8 and is the plug HKS recommend for the JDM DC5 ITR.