World No. 1 Dustin Johnson, coming off a runnerup finish in the Masters, held a one-stroke lead heading into the final round, but stumbled badly Sunday. Johnson shot a 6-over 77 — and he needed a birdie putt on 18 to do that — to tumble down the leaderboard to T28.J.T. Poston, Seamus Power and Kevin Streelman ended up tied for sixth at 9 under. C.T. Pan rode a 4-under 67 in the final round to pick up his first career PGA victory Sunday in the RBC Heritage in Hilton Head, South Carolina.The 27-year-old Taiwanese player, who turned pro in 2015, finished with a 12-under 272 on the Harbour Town Golf Links, holding a one-shot lead with golfers still on the course. He headed to the driving range to stay loose in the event of a playoff. But Pan clinched his first victory — he had a pair of wins in 2015 on the PGA Tour Canada — moments later when Shane Lowry’s 180-yard approach shot sailed wide right of the 18th green (Lowry needed to hole the shot out to tie Pan).Pan flashed a broad smile when informed he’d officially won.”It’s something when I was younger I always dreamed of,” Pan told CBS. “I watched Tiger (Woods) playing growing up. To have a W on the PGA Tour means the world to me.”It’s a dream come true.”Pan had five birdies, and survived a bogey on the par-5 15th to grab his first win, with steady approach shots like this on 18. One shot lead.One to play.C.T. Pan is dialed in. pic.twitter.com/EzWW8ufs0A— Golf Digest (@GolfDigest) April 21, 2019Matt Kuchar also shot a 67 Sunday to finish in sole possession of second, one shot behind Pan.Lowry finished with a 1-under 70 for the day to tie Patrick Cantlay and Scott Piercy for third at 10 under. Cantlay and Piercy both fired a 2-under 69.