Found online:
A. DTC P1491 - "EGR Valve Lift Insufficient Detected" is most often caused by a broken vacuum line going to the EGR valve. So I would check all the vaccum lines to be sure they are tight and not broken. Funny thing about vacuum lines, they never break out in the open, always behind or under something. Best way to check them is to remove them one at a time so you don't get mixed up and check them over carefully.
If the vacuum lines are good, you will need to check the electronics that operate the EGR system. It is an involved procedure, much too long to include here. Go to the library, in the Reference section, and get the Motors Import Service manual. That has the complete, step by step, procedure for checking the system. Or you can get a DIY subscription to Alldata which also has the complete, step by step, procedure.
this failure is from a voltage issue between the ecm and the egr valve. you need a shop to check this out as it may be a ecm failure. it is not as easy as you think.
Ron, it looks like this one has a linear valve, not vacuum according to alldata
Roy
you have to get them to clean the manifold out completely. they may have to soak it and then put it back on. put the new valve on and then they need to drill that hole that let the air and trash pass thru a little bigger so the air and trash can get out, hope this helps i had to have it done and i haven't had a problem since then. see if you can get a diagram of the manifold portion and take it to them if you think they will not be offended.
Since the online story stated both vacuum and elec I figured I covered both unless it was coked up again. Thanks for the updated input. That is why I said what I said in my bio. I have relearned so much on here. I really do appreciate it Roy.