Many Improved Familiars (e.g. ratling, imp, faerie dragon) have spell like abilities (SLAs). In each's default monster listing, it lists a caster level (CL) for them, e.g. (from ratling)
Spell-Like Abilities (CL 6th; concentration +7)
Familiar Basics changes a number of things for creatures that become familiars, including
Hit Dice: For the purpose of effects related to number of Hit Dice, use the master's character level or the familiar's normal HD total, whichever is higher.
Does this increased HD get used as the CL for the familiar's SLAs? Or does the CL always stay whatever's listed in the familiar's default stat block?