Well I went back to NAPA and they came up with two codes P1247 aND P 1248 -- NO TURBO BOOST AND LOW TURBO BOOST. So I figured that I blew up the turbo. I got home and opened the hood and found that the cold air side feed to the Turbo was separated -- evidently when it backfired it came apart. I put it back together and everything is fine. I just recently installed the boost gauge and really didn't know that 1 pound of boost wasn't OK. Now I got plenty. Thanks to those who responded.