Poor MPG after replacing head

How is everybody doing here?
Trying to figure out why my fuel mileage went down after replacing head on '09 Volvo D13, 820K, manual. The head was replaced 12K miles ago after I completely lost compression on 6th cyl, the exhaust valve seat was the reason. Along with new head did replace injectors, cups and wire harness. The cam and rockers were good.
After the job was done I experienced a noticeable drop in MPG. Right before breakdown I had 7.2-7.4mpg pulling a 30.000 at 65mph. Now I can barely making 6 under same load, speed and terrain. Slight vibration appeared at low rpms when accelerating. Almost disappeares after driving few hundred miles. Truck pulls pretty much the same as before. MPG shown is both the same from ECM and my own pump to pump calculations ( did pay attention to night idling as well).
Really frustrated because expected some gain in power plus AT LEAST SAME fuel consumption. Especially that compression test was good and truck is not using oil at all...
May be poor adjustments? Or being paranoic and all that is winter time related?Any ideas?
Thank you!

 

Boost is the same as before. Already pressure tested including intercooler

 

I remember the guys who did the work on head asked me to bring two shims 3.35 thick