Running rich

Helping a friend, 91 Fleetwood w/4.9L PFI. Car runs rich now that it starts (fouling plugs in 1-2 days). Fuel pressure is 48psi running and steady,KOEO pressure is 48psi but drops overnight.Injector rail is up and injectors are not leaking, all injectors are firing fine and computer seems to be working fine. Map,CTS, EGR are all working. Vacuum is low but expected with 250K miles. 2 other garages have replaced plugs (too many times),cap, rotor,coil,EGR. Plugs have no signs of oil blowby (only soaked with fuel), timing is reset to 10 degrees as the other shops thought 20 would burn the fuel. What would cause this to run rich? Fuel regulator even thou pressure is fine running? Fuel Pulsator or pump considering KOEO we get 48psi? Is there a prom update? Any help is appreciated, Thanks :banghead:

Low vacuum can cause it to run rich number one, check for fuel in the vacuum hose to the regulator, does the coolant temp sensor actually read the right temps to the pcm either in obd or with a scanner?

Yes, low vacuum can cause a rich condition.No fuel from the vacuum hose on regulator, yes CTS reads fine on the scanner and checks fine with resistance testing. Plugs are getting soaked with fuel (all look the same), injector pulse is looking fine on the scan also, and firing on the noid lights. I cannot find any vacuum leaks and is steady but low and intake isn't pissing oil or coolant ( for a tell tale sign). No oil on plugs at all.Compression was basically 180 across the board.Are intake leaks or cracks common on the 4.9?Thanks

Anyone with ideas?

Scan it for proper map sensor inputs and temp readings to the pcm. How low is the vacuum, partially clogged cat can also cause these issues.

Ding,Ding,Ding you are correct. Car wasn't running when I got it and after fixing Passlock, car dumped fuel. Everything on the scan was reading fine and in range but couldn't let run long due to fumes and smoke. We finally noticed the cat glowing red last saturday (universal junk).Vacuum was at 9" and now reading 13-14"(over 250K miles). Plugs are already cleaning up.The Cat totally slipped my mind to it showed it's red face. Thanks for the help Maxwedge