What spell/magic item/virtue/etc... helps a magus to increase his Lab Total bonus to research new spells (beside increasing Int, Art or taking the Virtues Adept Laboratory Student and Inventive Genius)?
An item which uses an intelego vim effect to confirm that the arts in use in the spell are the correct ones?
Spells and items don't typically add bonuses to the lab, except as detailed in the book Covenants. The book has guidelines for personalizing a lab that can improve labs so that they add bonuses to certain activities. Spells used of the TeFo of the item/spell/work being done typically don't provide a bonus, and any other bonuses are at the discretion of the SG, but there are some items also described that can be installed in the lab to realize bonuses.
Virtues that affect Arts, such as Puissant and Affinity are good, as well as applying either or both of those two to Magic Theory. Magical foci will add the lower of Technique or Form back to the lab total for spells that fall within the focus. Getting a familiar that is smart and teaching it magic theory will also improve lab totals, but this is a high investment, and has other added benefits besides just help in the lab. Assistants in the lab can be added, and is governed by your leadership score. By RAW, you can always have 1 assistant above and beyond your familiar, even if your leadership is 0. So a Leadership (lab work) 1 would allow two assistants, and so on. There is the similar spell bonus, where you add the magnitude of a known similar spell to the magnitude of the new spell being invented, and it applies to making items, as well. Verditius magi can add their Craft ability scores and those of their forge companions to their lab totals, and in certain circumstances for mysteries in their House, they can had Philosophiae scores, limited to the lesser of the actual score, Magic Theory, or the appropriate shape and material bonus.
Houses of Hermes: True Lineages indicates members of House Bonisaigus of the founder's line can have two more assistants than their leadership score would allow.