New plugs need to be checked and often need to be adjusted. If you bought anything other than a Volvo branded plug then it is likely used in multiple applications and may call for different gap settings in different cars.

For making the gap slightly smaller you can rap the electrode carefully on a wooden block, at least that is how my shop teacher showed us to do it many, many years ago. Of course you want to be gentle and not break the ceramic. If you go too far, you open it back up with the little notch type tool which is part of most gap gauges.

You want to set it such that the .30 wire fits, the .25 wire is obviously loose and the .35 wire will not go in.

John