P0243 code, popping noise

[A4droptop]

New to Audi, so please bear with me. Daughter's car was running fine today and then it made a few popping/ cracking sounds, threw a CES light, threw the EPC light, and wouldn't accelerate- like a loss of power.
Got it home and scanned it, and it came up with the P0243 watergate solenoid code and a few other emission codes- P0444, P2400, and a fuel pressure reg circuit P2294. Thought maybe the last three were set off by the P0243.
Fuses are all ok. Measured about 12 ohms at the waste gate solenoid plug.
Not sure what to do other than replace the solenoid- nothing in stock locally, so I have a few days. That thing is a bear to get to!
2007 A4 2.0t 83k miles.
Any ideas?

[A4droptop]

Replaced one relay under the ECM. Cleared codes, been running fine. Not sure what the popping noise was, but after I put it all back together, it was gone. Thinking it was maybe due to driving with the air intake off while testing??