Whew........watta PITA, though.
To start with, I followed the recommendations of the celicasupra forum members who have been down this path, and took everything apart to clean it.
The first problem came when I took the EGR valve off the "Upper Intake Manifold". The valve is held on by nuts on studs, and taking the nuts off freed the valve up, BUT the big line bringing the exhaust gas to the valve was rigidly mounted. The 27mm (!!) nut came off OK, but the rigid mounting of the pipe, and the studs protruding through the valve mounting flange, didn't allow for much movement.
So, like a dummy, I grabbed my BIG pry bar, and pried the valve off.
Guess what? The valve is made of very thin section CAST iron, and the threaded part had two sections break loose from the rest of it.
I used some good old, field-proven "JB Weld", and bonded the pieces back together. After letting it sit in the hot sun for several days, I cleaned the JB Weld off the threads with some jeweler's files, and used a sanding drum in my Dremel tool to clean up the back side where the inlet tube slides into it.
In order to put it all back together when all the cleaning was finished, and not fight getting the valve over the studs while trying to get it to line up with the exhaust gas pipe, I pulled the studs out of the manifold, chased the threads on both ends of the studs, the hold-down nuts, and the threads in the manifold so they'd all go together "finger easy", as it's a cramped spot to work on.
I knocked the core plug loose from the manifold at the passage junction where the exhaust gas dumps into the manifold via a small, pressed-in brass tube, and found the brass tube was plugged solid. I cleaned that out, and then removed the threaded plug from the back of the manifold, and ran a Hoppes 45 cal Bore Snake through the passage to clean it out.
BTW.....Hoppes #9 Powder Solvent works GREAT to remove baked-on carbon on car parts!
Then I took the "EGR Vacuum Modulator" apart and cleaned it, and cleaned up my now "repaired" EGR valve.
I started putting it back together last Friday, but got sidelined a bit with all the Memorial Day activities I helped with on the Iowa.
I put the cleaned EGR valve on the manifold loosely and got it started on the inlet pipe, and then run the studs in. They threaded in easily since all the threads were chased, and once I had the valve and inlet pipe aligned and the BIG nut kinda started, I put the nuts on the studs and tightened the valve down solid to the manifold.
After a bit of fiddling with the BIG nut (and a few choice words....), I got the inlet pipe tightened down, made sure the hold-down nuts were tight, and put the rest of the air-intake piping back on.
The engine started on the first crank and came up to fast idle. I put full manifold vacuum on the EGR valve, and the idle speed dropped like a rock, and the engine ran really rough, just like it's supposed to.
After it was fully warmed up, applying full vacuum to the valve makes it stumble and stall, just like my Toyota Service Manual says it's supposed to.
SO, even though the only part that "needed" cleaning was the little brass tube that channels the exhaust gas into the manifold, the whole shebang is now cleaned about as well as it can be without pulling everything off the engine.
Tomorrow I'll take her out for a good, long drive and make sure everything is up to operating temperature, and then head to the smog test place.
If she doesn't pass this time, I'll put a new converter on her, but the Toyota guys seem to think she'll pass, given as she failed on NOX, and the EGR system was essentially NON-OP.