bad running dt 466e help!

does any one have any answers as to why my 2001 dt 466 e 250 hp  has air coming out with  the return fuel so the truck is running terrible vibration no power and trouble shifting  because of low power its an (auto trans) i have had it to every garage in my area including dealerships... no help all they do is change parts i have spent 4000 dollars getting screwed . with no  help. motor only has 30,000 miles on it  can some one make a suggestion i can hardley run the truck now it,s getting worse by the day bock.phil@gmail.com thak you   phil...   i,m the one that found the air in the return. they could not tell me that either i have also replaced all the grommits in the fuel systyme is it possible for the pickup pump to put out 60 psi but let air in at the same time ??