What would people recommend pfr6b or pfr7b platinum spark plugs?

[Shazad]

Hi I have a Subaru Impreza wrx Classic 1997 import 

just deciding on what spark plugs to get as top end is misfiring Badly .. Taken out the pfr6b and put in the ngk iridium spark plugs ( this made it a bit worser as I'm getting a bit of a misfire on idle and on low revs low gears). 

Spoke to a specialist and he said I suggest you put a set of platinum spark plugs in . He said the ngk iridium are no good on these model cars? Is he right ?

what spark plugs shall I go for ?

pfr6b or pfr7b ? 

The only upgrades ive done on car are decat down pipe and a hks or filter . Any suggestions please .. 

[GeoffLeggy]

Has the car been mapped?  When were the mods you mention carried out?

[Shazad]

Hi the car has not been mapped 

the mods were carried out a month ago .. 

[GeoffLeggy]

Im just trying to see if there is a pattern with your decat and the issue.  It is mostly recommend to have a remap after decatting.  You might just need some ignition tweaks etc on a rolling road session.  You could try all sorts of plugs but you might not resolve the issue.  See if anyone else has any suggestions. 

[Shazad]

thanx geoffleggy