The exhaust is 3" turbo back with a flex section and a cat. Its pretty damn free flowing, so it supports the "damn cat" theory.

Looks like this:

 

how old is they exhaust? if the cat is 3" as well, event he cheap ones, shouldnt be clogged.

i am leaning towards the idea that its something else.

what tune do you have? Injectors? Fuel pump? FPR? Ignition?

if its not the tune, then i would think the fuel/ignition area for a weak link.

 

Are you sure you aren't running lean?

I mean I know you said it isn't the A/F, but are you sure?

 

The exhaust is several months old and has been running great up to this point.

The setup:
t25 from SR20, Megasquirt.. 550cc injectors 195hp pump with coil on plug setup. Again, this issue is not pinging from the motor. My cruise AFR is between 13.5 and 14.2ish on the AEM wideband, so it is even a little rich. Under boost it runs between 11.3-12 Its been too damn cold to work on the car the last few days, but I'm almost through pulling the turbo. I want to check that the turbine side wheel isn't jacked up. I also have a GT2871 to swap onto it so it serves a dual purpose. I ordered a magnaflow metal core woven cat to replace my ebay junker should I need to.

For the record: this is the cat that is in question
http://cgi.ebay.com/ebaymotors/3-Met...spagenameZWDVW

 

His timing map (built motor):




My timing map (stock block):





It wasn't his tune....running fine for months until he got it painted....it's either the cat or the turbines are fubaredddddd.

 

so what did the painters do to your car?
makes me think of...

 

Is it running red after no-boost cruise?
Is the manifold itself or exhaust side of the turbine red? Check in dim light.

I agree with the cat theory, if it's the downpipe...

Otherwise, I'd look for a timing screw up - low timing = high EGTs. Make sure MS is still commanding the right timing and your base timing matches what you see with the timing light.