Tsi_Xtreme

I'm having a problem. When I drive my car down the highway the a/f ratio is around 14.5. I'm now having a problem that seems to be getting worse. I'll be driving along and it will go from 14.5 down to 10.0 or lower and go super rich and flood out the car just about unless I hammer on it or get totally out of the gas. But even then it sometimes will stay there for a few seconds before it clears out and goes back to 14.5 or so. I've also noticed that I'm getting alot of backfire when i slow down now. I noticed it a few weeks ago but now after my last autocross it seems to be getting bad. I almost didn't get it home from the last race. Any suggestions?

I changed out the plugs thinking it might be that but no luck. I'm thinking it could be the coils or maybe a injector sticking.