American plugs are colder as the number gets lower.
Japanese plugs such as NGK or ND work the opposite. The higher the number the colder the plug. Not sure how Bosch does it but I'm sure a quick check on the manufactures web site will give you any info you need.
For the record, I'm using Autolite 43's on my last build. If I were using large doses of N2o I would run 42's, stock is 44.
Bbeep71, you are not running enough compression to have to run a colder than stock plug.