The EJ’s throttle body to intercooler hose is a notoriously shoddy design that rears its ugly head when you crank the boost up. So of course, shortly after reflashing with an Accessport, it started whistling like a tea kettle under full boost. The culprit was obvious: one of the hose clamp adjusters was so loose that it turned when I was simply trying to get the flathead screwdriver in there.
For now, the boost leak is gone! No more tea kettle in the engine bay. And perhaps this is placebo, but it feels significantly faster. Given how loose that hose was (ready to be pulled off if I wanted to) I bet I was down at least one or two PSI, AKA back down to stock power levels and just didn’t notice it. There are more cracks and pops on upshifts/downshifts now too, which also supports my hypothesis. More boost = more fuel!
The part is only $70 new and I’ll definitely be replacing it when I go for a catless downpipe/intake setup which involves another PSI of boost after the reflash. That will be around 320-330 at the crank, which is comfortably below the limits of the WRX 5 speed. I’ll be stopping there for the sake of the trans, and my wallet too.