The Grade 3, $1 million Delta Downs Jackpot got a boost last weekend when Gunnevera, who won the race in November, captured the Fountain of Youth at Gulfstream Park. In addition, J Boys Echo, who was fourth in the Jackpot, came back to capture the Gotham at Aqueduct. Chris Warren, director of racing for Delta, hopes the results will lead to a higher grade for the 1 1/16-mile race that in the past has been won by such horses as Exaggerator, Big Drama, and Goldencents. He said the results of last weekend’s Kentucky Derby preps were meaningful for Delta. “It gives us more exposure, more credibility for being a stepping-stone for the Derby,” he said. Delta will close out its Thoroughbred meet Saturday night with a pair of $50,000 stakes, including the Owners’ Appreciation Day, which drew Grade 3 winners Rise Up and Great Minds.