[e3sean]

it runs nice till go to open it up... if i slowly ease in to it it pulls but once i floor it it spits and chugs and sputters with the occasional backfire....

any thoughts i have the fuel pressure at 38 psi on my 38 lb injectors...

if i go get the tune will they fix all that??

 

[nba1341]

let it warm up?

 

[ryans88gt]

Some things I can think of for you to check...
Are you sure you have your timing set right? You should probably be running 12-14 base timing.
Do you have the correct spark plugs, electrode depth and heat range?
You are setting your fuel pressure with the vacuum port off right?
If you are setting it with the vacuum port still on the AFPR 38 at idle will be like 48 PSI at WOT.
And when you drive it you have the vacuum port hooked back up to a vacuum source?
Also, it might take some time for your computer to relearn the new setup.

 

[ryans88gt]

Also, check for codes, this might tell you if any of the sensors are malfuctioning.

Your MAF and injectors are the same calibration, correct?

If everything checks out, it may just need a good tune.

 

[dag545]

it runs nice till go to open it up... if i slowly ease in to it it pulls but once i floor it it spits and chugs and sputters with the occasional backfire....

any thoughts i have the fuel pressure at 38 psi on my 38 lb injectors...

if i go get the tune will they fix all that??

When I built my 5.0 it had most of the problems you stated above (bogging, cutting off, a little backfire, high idle). I got it running a lot better by just tweaking things like ryans88gt said (low idle, hard pulls, and no hesitation in the response). It was running strong and a lot faster than it was originally. Hell, I thought I did good, I was proud of myself until I saved money and got a chip/tuned. Then it was 100% accurate and most definitely faster.