I just had the exact same problem!
I had the O ring where the crossover pipe (the one that goes under the radiator) had a small nick out of it.
But the real problem is the hose that connects the pipe that comes up from the intercooler across the back of the engine to the intake manifold. This hose had a split in it that was allowing the air to leak.
I had all the O rings replaced along with the hose. Total bill was $151.05. The hose is $45, and there are 6 O rings, 5 of the rings are $4.40 each and the 6th one is $5.50.
Runs like a champ with no pressure leaks an no codes!