The only way to verify it is in fact a stc fitting is to tear the engine down to the high pressure oil pump. I take out the icp sensor and with a special tool i made that screws into the icp sensor port. I regulate anywhere from 30 to 50 psi of shop air through the system i dont use more than this because you can blow the seal out of a perfectly good pump, the pump has a weep hole in the back so you have to active/close the ipr so no air escapes,(using a Ford scanner) w/shop air holding pressure you simply just listen for the leak, if it is the stc fitting you can actually see if it is bad because you will see the air bubbling from around the fitting. I fabricated a fitting blockoff tool once you remove the pump to replace the stc fitting i can install this fitting to presure test the integrity of the rest of the system. Symptoms of a leaking stc fitting vary from say a blown stc fitting, if stc is leaking symptoms can be, hard long starts, starts ok cold,hard starts hot,stumbles under a load(presure loss) the pump usually can build 500 psi and overwhelm the leak, a leaking standpipe o ring can be the same symptom, where a blown stc fitting usually is a crank no start under any circumstance. If your dealer says it is the stc, insist they replace the standpipes with the updated part # all four of them!.
