I hope no mice first cel / electronic throttle control light came on at 750 miles lolWhat actuates the EGR valve? Is it a vacuum line or electric solenoid? If vacuum line check for any leaks in that line. If the EGR valve doesn't open as far as the engine wants it to or stays completely closed, it will act like a clogged EGR cooler. Also since there isn't the flow of exhaust gasses through the valve the boost reading will be off from what the computer expects to see. That will give you boost codes.
Question, how can you have a clogged EGR cooler if the code says "Flow too high"? Is it EGR flow or intake air flow? If EGR flow is too high that would be a sticking open or debris in the valve holding it open not a cooler problem. Unless the valve is part of the cooler
Do any of the OBD scanners give measuring block actual readings vs the requested value? I had a code indicating a turbo issue on a VW. Looking at the measuring blocks I saw the MAF value was fluctuating too fast but not too far out of spec to throw a MAF code. Sprayed the MAF down with electronics cleaner and problem solved. Sometimes the problem wont be what the code is indicating. The code is just what has been thrown far enough out of spec. The fuel pump was leaking fuel (thanks ultra low sulfur diesel) the vapor was sucked up the intake, hot wire of MAF burnt the fuel vapor and deposited sludge on the wire, at this point the not too far out of range MAF reading did not jive with the boost reading, confused the computer and computer thought the boost was the "implausible" problem. Boost control mechanism was perfectly fine.
Any chance a rodent has been under the hood chewing on things?