Ok so i'm trying to figure out possible reasons my truck is running so rich. Its a 4.8L engine. i've done the following to it:
220/222 110lsa comp cam
SLP valve springs
LS1 intake manifold w/ 28.8 injectors
Return style fuel setup
Walbro 255 fuel pump
Professional Products Fuel Pressure Regulator
SLP shorty headers w/ no cats into magnaflow round mufflers
Only front 02 sensors
Blackbear tune
Removed EGR and EVAP
Electric Fan
MAF right in front of the throttle body w/ cone filter in front of it (sticking right off the front of the engine)

Ever since I did this motor work its not run right. Its very rich. If i get on it if bogs out / shuts off briefly. It backfires really bad too. I'm already on my second set of plugs and thats just loading and unloading it on a trailer to go to maybe 4 shows.

It smells very hot when its running but it is probably the exhaust from all the extra fuel dumping out.

The fuel pressure goes down to almost 0 within a minute of turning the engine off.

I'm not 100% i have all the vacuum lines in the correct placement. I used the LS1howto.com as reference though.

I did have to extend the lines to the injectors, MAF, throttle body, 02 sensors.

What should I check? I plan on having a friend scan it tomorrow or friday but i'm affraid it wont help me here.