Texas BBQ Posse member Jim Rossman reports in from a quick BBQ run to Austin yesterday. You have to ask the question. Is the epicenter of the BBQ universe shifting north up Hwy. 183 from Lockhart to Austin? Posse pitmaster Marshall Cooper, his son Mark and I set out for Austin at 7:30 a.m. Our day’s goal was a return trip to JMueller’s BBQ and a visit to one Austin’s newest places – Stiles Switch BBQ and Brew. Our first stop was to pick up John Lewis and his fiancee Maureen. John is a fantastic competition pitmaster who also works…