Fuel lines are messed

hey, well i have just put back in my engine and everything. now when i start the car it runs like sh!t!! then i check around tha car and my fuel line is leaking badly.

i wanna know if its my fuel line that is causing my engine to run like shit.

some syptoms are:

-idles at 200 - 800 rpms
-lotta black smoke ( and i do mean LOTS!!!)
-shakes alot
-when i pull off my mafs it seems to run alot better (limp mode or something?)

well i tried adjusting my IAC valve and thats stuck at tha moment.

please note that when i took out my engine it was running fine. i just put it back it the way it came out. nothing was touched.***

OK now for tha main questions, how much are both to and return NEW gas lines from nissan or anywhere else?

OR

any ways to fix it?

thnx

curtis.