Chrysler Repair: 97 minivan runs poorly, mixture too lean only code, fuel pump relay, vacuum leak

Question
1997,tnc with 137,000,always well maint,3000mile oil change ect.7 months ago started having check engine light on with intermittent, shudder and sometimes loss of power but, never stalled. total tune-up car ran okay for a few weeks,again light reappears,changed up/down 02,ignition coil,fuel pump relay (running 63ohms)sometimes car running okay,then loss of power and it seems to almost seize up you can rev all you want (not sure if this is the famous limp mode)it ain't going no where very fast , wen it does go it's like a race car .I'm leaning toward replacing throttle,throttle sensor , as my next step after grueling day of fighting it to get anywhere a bottle of Lucas fuel injector, I managed to make it home.The only code I get is lean fuel mix I was told I had a bad cylinder by Goodyear-but when it runs it runs flat out well-I checked oil and it appears no contamination,no extra oil use,no color or odor change. PS I do get back fire when i am trying to keep it on the road at speed required , but when it catches that goes away

Answer
Hi Sassy,
Have you checked to see whether the egr valve is freely moving back and forth by using the tip of a screw driver in the slot of the stem to move it back and forth against spring pressure that tries to close it? If it is hanging up ajar that would cause a too lean fuel mixture. Try lubricating the stem where it enters the valve body with WD-40.  Also a vacuum leak would do that, so check around for possible cracked hoses/connectors. How about the PCV valve? Have you cleaned out the throttle body throat, idle air passageway, and both sides of the butterfly valve.
Those are things I would recommend to you. You might want to see what your compression readings are, or see what Goodyear gave as its reason a for mechanical problem. I would not bother throwing money at sensors without a code to direct your approach. Work on some of the above and then get back to me with any results.
Good luck in your efforts. I think you will find out what is wrong. Let me know which engine is in the van when/if you write back.
Roland