Anyone know where to find shops with good selections of spark plugs that carry lots of fitments and brands within Pasig area?

Planning to get Iridium or Platinum for my Opel, preferably Bosch or NGK. I think it's fitted with regular Densos pero after past 3-5 months pumapalya na and nasusunog. Probably an issue with the air/fuel mixture though still couldn't find the exact culprit.

Anyway going to try better quality spark plugs and see if there's any improvement...