Last ditch effort before I sell this piece?

[Smoker]

98 Jetta, AHU
The car Idles smoothly, but runs rough/misfires when you try to rev it.

Intake is clean

Replaced the following with used parts that I know were good:
-pump
-injectors
-ecu
-maf
-turbo

Other noteworthy pieces of information:
-P1550 is the only code that keeps popping up.
-static timing has been checked and rechecked multiple times, and injection timing is within spec according to vag-com.
-it was run on veggie oil for 60k miles
-the car definitely has wiring issues, due in part to hack jobs performed by the previous owner
-when I try to rev it, it's forcing an exhaust manifold leak that you don't otherwise hear... you can see it more than hear it. This specifically is making me wonder:

IS MY CAT CLOGGED??

I've heard of converters getting clogged to the point that a car won't even run, but I wouldn't have pictured it misfiring.

Any advice would be greatly appreciated!

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[CRSMP5]

simple test.. remove down pipe off turbo go for quick ride... rember fire.. so do not go far...

[Smoker]

Yeah. I just figured I'd fish for some advice while it's cooling down in the garage.

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[Smoker]

Well, that's one more thing ruled out

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[CRSMP5]

how much fuel pressure is there? may be needs hammer mod... or here is one.. make sure the out bolt is not pugged up.. it nopt flowing will do weird things.. bio/waste.. thats got goofy thing with cap nut.. make sure it clean..

[Smoker]

Well this is embarrassing... I decided is run a can of diesel purge through it to rule out fueling issues... I had replaced the filter once, so I was pretty sure that wasn't the culprit. It runs and revs fine with the lines going directly from the can to the pump. Maybe running diesel in the tank loosened up the veggie film and sent it all to the filter in a matter of a few hundred miles??

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[745 turbogreasel]

Ran on veg unheated in the main tank?
you almost certainly need to drop and clean the tank.

[8v-of-fury]

You almost certainly need to drop and clean the tank.

Almost certainly.. VEG oil is not as "awesome" or "easy" as people think it is, and needs to be set up properly or deal with the consequences unfortunately.

It is fairly easy to drop the tank on those mk3's so I would just do this.. as it is more than likely your entire issue with running that oil in the main tank.

Short of that.. I'd replace the filter with a cheap one and run it through a full tank of diesel with some cleaners in there.

[Smoker]

Trust me, I know it's not awesome or easy. I never would've set this car up the way the po had, and I only bought it because it was way cheap.

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[CrazyAndy]

Couldn't you just run the tank dry, dump some bio-bor in, shake the back end up, and pull out the crud with a mity-vac through the feed line pre-filter?  It's what we techs do when dummies put gas into the new CR cars, except without the bio-bor thingy.

Oh and hi fellow old dominioner; Charlottesville up here!

[745 turbogreasel]

No, you need to get in there balls deep and clean.more than likely the prefilter is clogged with stuff, and there is another handful waiting to grab on.

[Smoker]

No, you need to get in there balls deep and clean.more than likely the prefilter is clogged with stuff, and there is another handful waiting to grab on.

Yep, I did all that. Unfortunately it had deeper problems than that. I kept what I wanted of it and sold it barely running.

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