2004 Silverado 2500HD wont start

First the old stuff because I am still looking for some help/info. I bought a 2004 Silverado 2500HD 4x4 with
a 6.0 vortec engine in July. I drove it about 30 miles home and it ran great.
A couple days went by and when I took it for a ride and it started stalling.
I got it back home and it hasn't run since. Well it will run for a few seconds
but then die. Ok so here is what I have do to it. First I changed the plugs
and wires, still nothing. I checked fuel pressure and it rose to about 60psi
but the imediately went to zero so I changed the fuel pump. Still nothing. Then
I changed the crank position sensor, still nothing. Then cleaned the throttle
body and nothing. Oh I forgot to say that I was at no time getting any codes
on the diagnostic computer. After cleaning the throttle body I got a p0101
code(maf sensor) so I changed the maf sensor. Still nothing so I put a new
throttle body on it. Now I get codes P0068,P0101,P0107,P0220,P1516, P2135 and
the odometer says reduced engine power. And of course it will start to turn
over but it will not actually run. All these codes pertain to the throttle body
, maf, map and acceleration pedal position sensor but I am not sure where to go
from here. Do I need to change the acceleration pedal position sensor and the
map sensor? They are the only ones I did not change. Or do I need to tow it to
a garage for some kind of calibration or just take the PCM in and have it
reprogramed?I am really at a loss here, so any help would be appreciated. Also
just an FYI this truck doesnt have a external fuel filter. It has a non servicable
permanent filter in the fuel pump and the fuel pressure regulator is also on the
fuel pump. Ok now on to today. Turns out the throttle body I bought was junk so I returned it. I changed the pedal sensor and that did no good so I took it to a dealer and after 6 hours of working on it they have no clue as to why it wont start so I brought it home.The dealer was the one that said the throttle body was no good and they were right. when I put on a different one all codes went away, they also said fuel pressure and spark was good but I checked and cleaned all the gound connections that I could find and replced the ground cable from the battery. Still the thing will not start. Now all the sudden I have no spark. I checked at the plug and I checked 3 of the 8 coils. No spark from any of it. Anybody have any ideas.

first thing is you are in the wrong vehicle forum. the silverado forum is where this should be posted.

the fuel pressure should hold on engine shut down . replacing the fuel pump was correct. what pump did you use I hope not airtex. most find that the delphi pumps are long lasting. airtex can be bad out of the box like the throttle body you purchased.

with the original problem engines starts for a very short time then stalls . this I find is the security system . what ignition key are you using ? what is the security light doing.

move this to the silverado section if you still need help.