ls67ss

hello i have this 96 e320 with the inline 6 and automatic that the engine light and check electronics light are on scanned found a po400 found bad vacum lines replaced test drove and about 20 miles in the lights came back on.scanned again and there is no codes so not sure what direction to go trying to get it through emmisions and with engine light on its a no go.the vehicle runs great drives great has no codes in history or stored in faults.and the other issue with the vehicle is the instrument cluster guages intermittently work .any help with either would be apreciated my priority is getting it through emmissions thanks

FlatlineEF9

My 96 recently had a similar situation. P0400, i changed my vac lines and the light went away for 2 days. Light came back on, but no codes via scanner. Replaced all 3 coil packs and CEL is gone.

Gavin Viney

Could be a stuck open egr, i take it is diesel. An egr stuck open will cause you boost to be lost and black smoke from the exhaust.
Blank and a remap to remove the egr in software will sort the issue.