I thought i would change my plugs in my s3. I got a set of denso plugs from epc, part number K20PR-P8. Now i took my olds plugs out and they were a small thread which goes into the coil packs. The new ones are bigger at the end, amd you can not unscrew the caps. Are the denso plugs wrong? or are the plugs which are in my car wrong?