Guru releases 1st-quarter portfolio. : Billionaire investor Carl Icahn (Trades, Portfolio) disclosed his firm’s first-quarter equity portfolio earlier this month. The guru’s Florida-based firm, Icahn Capital Management, is known for taking activist positions in struggling companies and working with management to improve profitability as well as unlock value for shareholders. The 13F filing for the three months ended March 31 shows he entered a new position Illumina Inc. (ILMN, Financial), which is a recent target, as well as added to his stake in Southwest Gas Holdings SWX Inc. (SWX, Financial).