5.7 mpg loaded or empty

But that wouldn't explain the vibration on acceleration or with using the jake brake. If it was the manifold or the sensors the ecm would have given codes for the failure of them.

 

Actually if that intake was seriously plugged, or if the exhaust was seriously plugged it very well may shake. BUT, what I suggested is a DIY, cheap stab at a potentially larger issue. $150 dollars for the IMAP and DELTA-P sensors, a day of down time and about $40 worth of carb and choke cleaner. ECMs are not as smart as we all think them to be. When I first started doing those annual tune-ups my sensors were completely CARBON PACKED. No CEL.

 

didn't think of that. Good idea though.

 

Early D13 engines had a problem with the copper injector cups, IIRC. They've since switched to stainless injector cups to resolve the issue, If your engine hasn't been updated, that may be the problem.

 

Time for a injector "pack" and the updated stainless cups, installed with the new Volvo cup tool.

 

You need injectors and cups. Care it to a dealer and have them do the "air in fuel test" it will bypass the return line from the front of the head to the fuel filter housing and run straight from the head to the tank with a clear line. The tech should let it idle for around 5 minutes minimum to eliminate any air introduced in to the fuel system. If it does have copper cups then your definately running on "hopes and dreams" and even if not Volvo supposedly had a "bad batch" of injectors and also they had a TPI where they do away with the bottom o-ring on the injector thus only leaving the top o-ring on the injector (sounds crazy I know), so if you have stainless steel cups & injectors with 2 o-rings and not 1 then they're outdated as well. Also the "special" cup tool is no fun to be on the other side of. Hope this helps some.