A street performer gains a bonus equal to half his level on Bluff, Disguise, Knowledge (local), and Sleight of Hand checks, Diplomacy or Intimidate checks made to influence crowds, and Diplomacy checks to gather information (minimum +1). This replaces bardic knowledge.
From Versatile Performance (Oratory - replaces Diplomacy):
He can use his bonus in that skill in place of his bonus in associated skills. When substituting in this way, the bard uses his total Perform skill bonus, including class skill bonus, in place of its associated skill's bonus,
Say I have a level 8 bard with an Oratory bonus of +18. Can I add the additional +4 from Streetwise to gather information as per Diplomacy, to make the gather information modifier a +22?