volvo epg1 problem

new problem on volvo 2004 d12d volvo engine .epg1 message comes on I notice some kind of air noise from turbo when i accelerate.I called dealer for price on the epg its $900+ us and 550 for the epg air valve.what will be the correct way to check . i read in another forum u apply air to epg and whatch if it closes.what about the air valve how is this check I will hate to replace the 2 units with out needing to.what issues might this cause. thanks for any help

 

mid 128 sid 146 and mid 128 ppid 124 thanks for respond pablo

 

ok so how can I check the epg1 and air valve price for this are kind of high epg is $950 and air valve that controls the epg is $550.if it helps I do hear air from that area every time I accelerate .this sound started about the same time I got the epg message.