knocking mustang 5.0

[5150coupe]

i ended up finding out that it was just a timing issue. just backfiring...but now i have a couple other related issues. i can't seem to set the timing to 14 like it was before. at 14 i get backfiring and it won't idle or run well unless it is advance way to high at about 22-25. it doesn't seem to ping even though it is high, so i thought maybe the timing marker is off or something, but it looks to be at the same location as my friends coupe. i'm going to put it on the computer and start checking codes.