decarbonize?

[toddmpa]

Hi. My '01 Rodeo 3.2 V6 loads up after idling for an hour or two. (You have to drive I-95 to recognize this as a problem.) It then suffers erratic idle, modest bucking under acceleration, no CEL, but a white-knuckled wife who wants something done now.
I replaced O2 and mass air flow sensors, the EGR valve, spark plugs and air cleaner. (No timing belt yet although it is due at 102k.) The plugs were a lovely tan. The EGR valve was bad. I found the intake manifold gasket problem and had it replaced under warranty.
It ran really sweet until I found yet another construction zone in Maryland. I sprayed a can of B-12 down the EGR port, which worked until Saturday, when I got caught behind a one-car flip and roll in Delaware.
The dealer wanted to decarbonize it for $180. I declined, suspecting that the service manager wanted me to pay a second time for IMF work they were billing to Isuzu. Afterward I asked the service manager, so your mechanic walked the plenum cover over the parts cleaner, right? No, he said.
My questions: Was the dealership right that my problem is gunk on the throttle bodies to a degree that spray cans can't handle?
The dealership was pitching a chemical flush applied through the air intake. I've found private garages that will do it for a third of what the dealer wanted. But they say that carbon in the combustion chambers is the usual culprit, and that 99 percent of the time, it is a symptom rather than a disease. (Translation: leave your checkbook on the passenger's seat.) Worth the fight to have it done?
Is DIY Sea-Foam or equivalent an alternative?
I have searched this site many times as a lurker. My apologies if I have missed earlier answers.
Thanks
Todd

[amigo-2k]

did you clean the EGR tube where is exits behind the throttle body plate?

[toddmpa]

If you mean spray down the bigger hole that directs exhaust into the EGR, the answer is no.
I am a UW Madison alum. Got Bucky Badger on my rear window. Something of a problem with the JoePa admirers around here.

[amigo-2k]

intake after 80K

http://isuzufaq.ibctech.ca/inside.pdf

Look at the second and third photo for the EGR pipe:

http://www.automotiveforums.com/vbul...58#post1777258