Recommended Spark Plugs for 99 STI
 

Can anyone recommend a particular type of spark plug for my 99 STI. The ones that were in the Japanese imported engine were NGK Iriway 7's

Depends, have you modofied your version 5 sti? Usually NGKPFR6B's for a smaller boosted cars and NGKPFR7B's for higher, more intense boost orientated engines.

The car is modified quite heavily. Mods are as listed,

Apexi Power FC
VF34 Turbo
AVO silicone Intake
Equal Length Headers
Blitz Dual Stage Electronic Boost Controller
3" Turbo Back Exhaust
06 STI Top Mount Intercooler

Few other mods but those are the engine performance mods. Do you think the NGK 7's that came with the engine would still be ok to use. Or just get new ones? Not sure what the life span on those plugs are.

Found these HKS ones on ebay. Are these any good?

[url]http://cgi.ebay.com.au/HKS-SUPER-FIRE-RACING-SPARK-PLUGS-SUBARU-WRX-STI-GC8_W0QQitemZ130303675969QQcmdZViewItemQQptZAU_Car_Parts_Accessories?hash=item130303675969&_trksid=p3286.c0.m14&_trkparms=66%3A2%7C65%3A1%7C39%3A1%7C240%3A1318%7C301%3A1%7C293%3A1%7C294%3A50[/url]

NGK Platinums .. My car has similar mods, no problem. How much boost? I'm running 20psi .. It's more about how much boost/timing your running i think to choose a plug?

As above with them mods pfr7b's :) :)

I had pfr7b's in my car as it had a problem where it would surge on boost. the pfr7bs sorted it out, at my 100,000 6b's were put in and i believe the surge might be back on WOT.

So the 7's are the same as the ones I had in there. NGK iri 7's

genuine subaru? i think ngk platinums...??

i am sure the ngk pfr7bs are platinum???....