I would check to see if the boost line and banjo bolt from the intake maniflod to the ALDA on the pump is clogged first. The line starts from the very back of the intake manifold and runs behind the valve cover to the firewall I believe and then to the "thing" on top of the pump. If that doesn't fix it you can take steps after that but that's the first thing to check other than filters.

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1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k