1994 6.5 diesel won’t rev over 2500 rpm

[Maedale]

Engine only revs to 2500 on the road. If you hold accelerator to floor will pour black smoke. If you let off it will shift and get up to highway speed
Lift pump wired directly to 12 volt
installed clear fuel line and shows no bubbles
have 6 psi fuel pressure at bleed valve and drops to 4 on acceleration
there was no last ditch screen in front housing
Rebulit injection pump installed in last 10000 km
cleaned grounds at rear of engine
disconnected wire to optical sensor and engine died then changed crank pos sensor
no difference in performance with air cleaner removed
engine was completey rebuilt less than 5000 km ago
have tried different fsd with same results
as fsd is remotely mounted also plugged in directly to inj pump to rule out ext cable
Wiring harness changed to inj pump

any ideas would be appreciated