Help baffling CE light 98 E320

Here's a strange one.... I'm at my wit's end; I beginning to hate my car.
1998 E320 w/ 65,000 miles. CE light illuminated with error codes P0107 &
P0173. Started with a new gas cap. No help.
Went to an independent MB-German car mechanic who, over the course of a couple of visits, gave it a carbon blaster induction treatment, 4 new O2 sensors and a MAF sensor. The acceleration was greatly improved; it's a rocket. The idle is steady, no problems. The car appears to function normally.
But typically 25 miles after erasing the codes, the CE light illuminates with error codes P0170 & P0173. It appears to only illuminate at slow speeds, particularly after a spell of highway driving.
The mechanic and his assistants were reassuring they could fix it. They said there's a chance the O2 sensors were damaged by the CO discharge after the carbon blaster treatment (the weather at the time was quite cold; it was difficult to get the engine & catalytic system hot, he said). He's offered to do what it takes free of charge.
That said, assuming there's no vacuum leak, what could be the source of the error codes? Thanks in advance for your suggestions.
I'm facing deadline for the NJ Clean Air inspection so, again, thanks in advance for your help....
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
P0170 and P0173 are fuel trim codes, one for idle and the other for part throttle. The adaption at idle and part throttle has reached the end of its limit. That is part of the answer. However, your mechanic is not saying WHICH end of the limit! Most of the time, the MAF sets P0173 because the part throttle adaption has reached the end of its LEAN limit, the LEAN limit is 1.32. But P0173 can be set if the adaption reaches the RICH limit. If I remember right, it is 0.62 but it may be 0.82. Very rare to reach this unless you have an injector pouring gas in a cylinder. Since you have both trim faults, have him get a print out of the freeze frame of what set the failure. Self adaption works up to a point. It will lean a rich running or richen a lean running engine up to its limit. But you need to know what it is trying to accomplish. If you are too rich, it will try to lean it. The weakest link for too rich is the pressure regulator on the fuel rail. Shut the engine off and pull off the vacuum hose that goes to the top of the regulator. Is it wet with fuel? Let it sit and watch it. Does fuel dribble out the nipple? If the lean limit has been reached and the self adaption can no longer richen the engine, check for vacuum leaks. 2 prme contenders are the purge valve [stuck open] and the shut-off valve on top of the charcoal cannister [stuck open].

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I cc'd this to you. I got an auto response that I would need to go to another link to get you to accept my email?!? Screw that.....if you get it, fine; if you don't, read it here....

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks, Karl. I read your post here. I watched him run a diagnostic on the car with a handheld computer that plugs into the port under the hood. I didn't recall the fuel trim limits so I will check that out.
Another question: After a MAF meter install, would ONLY the MB dealer be able to reset the fuel trim adaptations or would my independent be able to do it with his computer unit?
Thank you.

car.
P0107 &

a
O2
a
illuminates
They
after
it was

offered
of the

in
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
You should not reset the trim. IF the MAF is the culprit, then a 10 mile city drive will show the adaption moving back to center: close to 1.00. This is a good test to see if it is fixed. If his scanner shows fault codes only and no actual values, then he is just guessing with your money. This is the SWAG method of repairing cars.... one step up from the Mossberg method.
[SWAG is Scientific Wild Ass Guess...... Mossberg is load up the shotgun and throw everything at it, you may get lucky.....]

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
No, his scanner, a Snap On, and shows far more than simply fault codes. It's quite extensive, with page after page after page of detail and readings.
Thank you for your replies.

my
of
new
it's
function
slow
discharge
cold;
source
thanks
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.