P0171 code

Hey everyone,

I have recently bought a 2005 A4 B7 2.0 tfsi quattro, BGB engine if it makes any difference, 85,000 miles on it and keep getting a P0171 code.
The code first came up about 100 miles after i bought it. After a rigorous search through many forums for some guidance i searched for vacuum leaks but couldn't find any, so changed the PCV Valve (non OEM) and attched hoses, erased the code and carried on.
The code came up again after about 30 miles of driving. This time it developed a misfire which was quickly rectified with a new coil pack. I also removed the MAF and cleaned it. I again removed the code and this time the idle speed came down from around 800 to about 750 (which i've read is correct). The car seemed better but again after around 30 miles the code re-appeared.
I searched again for Vacuum leaks and by luck found that the check valve coming off the brake booster had an open hose prong. I bunged this and removed the code again.
The brakes instantly felt better (no suprise really) and the car feels a lot more responsive and boosts a lot better than before. Even the wife has commented on how different it feels.
But again the code has come back. I know it could be any 1 of a few different things but i need it sorted and haven't really got the time to put in the garage. I'm fairly good with spanners so i can any jobs myself.

I have taken a freeze frame of when the code last appeared with a half decent obd machine.

Any help would be appriciated

Many thanks

Keith