1997 pickup sputters, sometimes won't idle

[chicojerry]

Hi - My 1997 Nissan Pickup (KA24) starts fine, but when warmed up will begin sputtering like it isn't getting gas, run fine, sputter, etc. Sometimes it will die when I stop (but start right up), but sometimes will idle fine. When in its rough running mode, it also seems to be real rich (black exhaust). Doesn't show any computer codes (computer gave me a 50 -5 - five long flashes, 5 short ones when I ran the self diagnostics). I've changed the spark plugs and wires, fuel filter, fuel pump (even though a pressure gage showed 35 lbs when the pressure regulator vacuum hose was connected and 45 lbs when I disconnected the regulator vacuum hose). I could find no bad vacuum hoses. Since the computer isn't showing any codes, I would think this indicates the electrical sensors are good. So ... how do I track down this problem?

Thanks