General: Help

[Roundmanx]

Hi guys need a bit of help had a bit of a problem for a while where my 2005 xc90 d5 awd euro 3 engine only done 122,921 has had what seems to be a popping sound if I take the oil cap off and seems very under powered
So i have replaced
All engine mounts
Maf sensor
New egr valve
Exhaust and cat been done
Crank sensor
Fuel pump and level
Turbo boost solenoid
Air intake control valve
Glow plugs
I then smoke tested her and found a leak from the intercooler so that has been replaced today smoke tested again no leaks but she has a bit more power and no popping when take oil cap off but she is still not back to full power still lagging will get to full speed but takes longer turbo is quacking in all gears change as normal just no power where can I look next was thinking rocker arms and lifters but she is costing a fortune and hoping there is possibly something cheaper and simpler to look at first any suggestions thanks in advance