Parts cannon to the extreme?

Hey guys. Looking for some info here on a 2013 Cadillac XTS with the 3.6l that we are currently installing a new engine in. Car has 185k miles and was at the dealer for a CEL issue. From what the customer told us is the dealer stated the timing chains were stretched and qouted him a price he didn't like. He ended up contacting us, he already purchased a junk yard engine with 40k miles on it and wanted us to throw it in. Of course no warranty there but he didn't care he figured he's gonna come out ahead on this either way. I pulled the car in, rear tires have cords showing all across so I wasn't gonna test drive it but pulled codes to have on hand.
We have. 
p0011- Intake cam performance
p0017-crank/exhuast cam 1 position not plausible
p0019-"       " cam 2 not plausible
p0020- Intake cam solienoid control bank 2
p0021-Intake cam performance bank 2
p0097-IAT low volt
p0107-MAP low volt
p0113-IAT high volt
p0300-miss
p0430-Cat effiecncy bank 2
p0443-EVAP purge control circuit
Since this was already "diagnosed" and the customer is refusing to replace the bald tires we're just doing what we're told and sending it out. I got the engine and trans on the bench and started swapping parts over, I pulled bank 2 cat and it's totally gone, down stream after the Y pipe is completely plugged with dust and debris. This car did start and run ok into the shop but mind you I never test drove it because of safety concerns. My question though now is would a plugged exhuast cause timing codes? I'm leaning more towards this just needing a CAT and a cleaning rather then a whole engine (well timing job) but would like to know what others have seen out there. Quick google search is kinda 50/50 on this. Am I thinking about this all wrong?

My question though now is would a plugged exhuast cause timing codes?

No. Catalytic converter problems will not set timing codes.  A clogged cat/exhaust can cause a loss of power, and...

I pulled bank 2 cat and it's totally gone

That explains the P0430, but not the timing codes. 

With all of those codes you have more going on than just Cam Timing and Cat problems.

Focusing on the Timing codes, these are all VVT performance codes, rather than correlation codes. 
The one that I would focus on first is the P0020.

Conditions for Setting the DTC
The ECM detects that the commanded state of the driver and the actual state of the control circuit do not match for greater than 5 s.

Since you have, already, pulled the engine, I assume that you do not want to do any testing, right now. 


 

Thanks for the info and yea I guess that makes more sense, I guess when I seen the p0011,17,19 and 21 codes I start thinking that maybe with the plugged exhaust that the ECM was advancing or cutting back timing trying to stay running but couldn't counter the plugged downstream thus setting the codes. Yea I'm not a fan of taking on these jobs of "last shop said it needs XYZ, i want you to do XYZ, no diag". We ended up installing a tranny in a e series a month ago because the customer said it was bad well after the new tranny the thing was gutless as could be and we found the drivers cat had fell apart, after talking to the customer turns out he thought it was stuck in gear and needing a tranny.
I should be done with the motor swap later today and we'll see how it runs, customer is refusing tires in the rear and to replace a blown front cv axle so we're just gonna get it running and do our best to be sure it starts and runs fine in the parking lot and call it good, bout all we can do at this point. new engine with "40k miles" has extremely carboned up valves so I'll take a little time getting those cleaned up. So far looking at the harness I see no visible signs of damage, dealer lost quiet a few fasteners and hose clamps but no damage as far as I can tell.