Car was running fine then just started going haywire

[2+2 280z]

i just rebuilt the engine on my 77 280z and it was running good for 2 months timing was to the tooth and and did not smoke sounded healthy. then i came out one day and it wouldnt start. and whe it did it smokes blacke really bad and it misses really bad when you throttle it up. I have to floor it sometimes to even get the rpms to go up. Ive changed the coil have no vaccum leaks and changed the throttle positoning sensor and still no luck i need help. please any advice is appriciated

[Pomorza]

For what I remember black smoke means that your running rich. Start with the basics. Check the fuel pressure and check the plugs, check the oil. (see if it smells of fuel). Check that your wired the coil right.

Hope that helps

Jan