2000 stumble/dies-no code problem

hello! truck problem- starts fine then, might be 2min, or maybe couple days, engine will die. USUALLY it will start right back up in neutral & I can keep going. Becoming more often though,I have to shut the key to off, wait a few seconds then it will restart. sometimes i have to wait maybe a half an hour for it to restart-if I smell gas while cranking(like the choke was closed-& yes I know it doesn't have one)I know it will have to set a while to restart.
also while driving it can have an irratic hard stumble-maybe 1 or 2 kicks but doesn't die then.
I have a code reader but not a scanner. the only code it has shown was for a map sensor(108) & i replaced it- running voltage way off(haynes man.)

2000 4wd 99k mi. approx 3k ago,new cap, rotor. wires & plugs (ac's) & 50 mi ago map sensor. replaced intake gaskets aprox.5k ago.
removed top of intake last week & all was pretty clean- no spots cleaner than anywhere else. fuel pressure runs approx58psi all the time running or stopped & always has for 2yrs I've had truck. pressure doesn't bleed down after it is shut off.
anybody got any ideas or suggestions?
THANKS

Engine running fuel pressure means very little, there are too many variables involved. However, 58psi while the pump is running and the engine is off is too low. Fuel pressure is not monitored by the On Board Diagnostic (OBD) system and therefore cannot set a Diagnostic Trouble Code (DTC), or illuminate the Service Engine Soon (SES) light.
Fuel pump operation:
The fuel pump circuits are designed to energize the fuel pump through a relay continuously any time the key is in the START position. When the key is in the RUN position the fuel pump will operate provided the engine is running. If the engine stalls, or is not running for any reason, the PCM/VCM will shut off the fuel pump after approximately 2 to 3 seconds.

Fuel pressure test:
Install the fuel pressure gauge to the test port near the distributor. Turn the key to the RUN position but do not start the engine. While the fuel pump is running, fuel pressure must be 60-66psi. After approximately 2 to 3 seconds, the fuel pump will shut off. Fuel pressure must remain between 55-60psi for several minutes. A drop in pressure below 55psi indicates excessive leak down. Possible places to leak are the fuel pressure regulator, the fuel lines under the upper intake manifold, a fuel injector that is stuck open, a leaking fuel line or connector, or the check valve in the fuel pump assembly.

Here is a link to an inexpensive, and adequate fuel pressure tester: http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=92699 Accurate diagnosis of an internal fuel leak requires additional test equipment. In some cases it requires the removal of the upper intake manifold.

Hope this helps.

I do have a fuel pressure guage. the pressure (58 psi at "run"- not started. & pressure does hold fine) hasn't changed in the 2yrs i've had the truck-& it has always ran fine.
this new problem has only been happening for a couple months.
I did replace the regulator about 1yr ago also

update- dies more often now. rechecked fuel pressure- key to run, press. goes to 61 while pump is running then drops to about 57-58 & holds. idles at about 52- jumps to 60 when i hit the gas (within Haynes manual specs).
when truck dies,pressure stays up- doesn't fall at all. rest of truck does not shut off-guages ,lights, radio etc.
and still no codes.....
any ideas??

I realize you have replaced the cap, rotor, wires and plugs... just for S&G start the engine and use a spray bottle of water and put a mist over the cap, wires and coil. Doing this after dark may show some stray sparks... just a thought.