The court-ordered auction for the parent company of Citgo just got more interesting as the former preferred bidder has to sweeten its offer to stay in the race after the emergence of a surprise rival. Earlier this week, media reported that a company affiliated with hedge fund Elliott Management had emerged as the frontrunner in the bidding for PDV Holding, a PDVSA unit that owns U.S.-based Citgo. The new bidder, Amber Energy, had beaten the offer of the consortium led by miner Gold Reserve, which had previously been considered the best one of all.…