ok so i have a 5.7 350 fuel rails are all stock with stock injectors. im not sure but someone told me they were very reliable and that they were very low psi. so i was looking at getting something like this. http://summitracing.com/parts/BBK-17...RO&prefilter=1

and this
http://summitracing.com/parts/ACC-150832/

my question is how hard is this going to be to put in and how much horse power and im going to gain from doing this. cause you can adjust the regulator so say 46psi any information would be great.

 

Unless you are retuning the ecu because of changes to the engine you should not mess with the injectors or regulator. The car uses something like 39 or 42 psi. If I had the oppertunity to do mine over again I would never have installed the adjustable regulator.

 

Your running stock, the injectors are to big. Use your money
and get the larger runners and base to match and a good cam, then
make the other changes, also burn a new chip

 

I agree with the others, those injectors are way too big and your car will run like crap. The fuel pressure regulator on the other hand, you can get that without retuning the computer. I have that exact fuel pressure regulator and have no problems. You can bump up the fuel pressure, maybe one or two psi if you have made other engine mods. As far as installation of the afpr, check here for answers...here