For some reason in that last post I stated it didn't have a cold start valve, but it does. I deleted that to avoid confusing anyone. There are three lines on the regulator, if you loosen any of them fuel will come out. The one that comes out at the end returns fuel back to the tank, the large port on the side is the fuel into the regulator from the fuel distributor & the small one on the side I think is a feedback to the differential pressure regulator on the fuel distributor. As I stated any diagnosis of these components requires a special CIS fuel gauge set, I've seen them for around $100. Also, you would probably need a special wiring harness adapters for the differential pressure regulator. That is how you adjust mixture & check operation of various components (O2 sensor, potentiometer, etc...). A couple of other things I thought you could check yourself is to pull the cold start valve when the engine is hot & make sure it is not spraying when you crank the engine. You can also spray starting fluid around the base of the injectors to see if the seals are leaking, see if the engine RPM's change.