By Jessica Toonkel, Olivia Oran and Ross Kerber (Reuters) – Institutional investors who met with Twitter Inc this week say they are optimistic about its initial public offering and see little sign of the irrational exuberance that preceded Facebook Incs splashy coming-out party in 2012. On Monday and Tuesday, Twitter Chief Executive Dick Costolo and Chief Financial Officer Mike Gupta met with large fund managers and analysts in New York and on the East Coast to sell them on an IPO that seeks to raise up to $1.6 billion for the loss-making social media company. Closely watched by Wall Street and Silicon Valley, Twitters relatively conservative offering has differed from Facebooks $16 billion IPO in a panoply of ways, from its vastly smaller deal size to a decision to list on the New York Stock Exchange over Nasdaq. It definitely was different than when (Facebook CEO Mark) Zuckerberg came through … Its the right kind of buzz, said one fund manager who met with Twitter on Monday.