Which Addon Does This?
 

the grey numbers for item level, i would really like to control it's font size or use a MOD key like [alt] to display them, they are kind of in my way.

Might be the actual bag addon.

That is the same bag mod I use called Adibags which has a large number of options for configuration. For the ilvl options look type /adibags then look under Plugins>Item level.

It is actively maintained by the author and if you have any suggestions let them know on wowace via the ticket system.

There also was an addon to show it in the normal blizzard bags but can't tell the name now. something like shlevel or so

!Sylevel is probably the one you're thinking of.

Yep thats it, odd I remember the color of the name but not its name :D

Not too odd... the color, and the author's snide reply when I asked them to remove it so their addon would appear where expected in the alphabetical listings WoW uses to display addons, was why I quit using it and just wrote my own.