1988 Nissan 300ZX rough running and alot of exhaust smoke

Hi I have a '88 300zx 2+2, I just bought this car off of an old lady and nothing has been done to it except regular maintenence so I bought all the tune-up parts and a timing belt and tensioner. Before doing any work to it the car was running fine. My friend is helping me out because I dont know nearly as much as he does but on the other hand he has not had much experience with 300zx 's. Back to the problem we put everything in. Ngk spark plugs, ngk wires, distributer cap + rotor, fuel filter, pcv valve, air filter, and then the timing belt and tensioner with the spring, also put a valve cover gasket set on because they were leaking on the left and also got a plenum gasket because we had to take it off to get to the valve cover gaskets. After the timing belt was on and everything was lined up we started it and it ran really rough and there was alot of smoke coming out of the exhaust when we stepped on the gas pedal. Figured we would take it around the block to see what happens. Did that and it was smoking (grey smoke) unbeleivably and all of a sudden there was a semi-loud knocking noise so we brang it back in the shop to take another look but cant seem to figure anything out. The timing is lined up so thats not an issue. I left the car with my friend and he worked on it during the week and he spliced a couple of fuel injection wires and it runs a little better but not nearly were it should. He seems to think its some type of fuel problem were its getting too much fuel but he still cant find the problem. Has also taken the spark plugs out to see if they were bent but they were fine except they were really black, and am not sure what this means. I have searched for recalls online and found that there was a fuel injector recall but am not sure if the lady ever had it done. This is my first time here I just happen to google you guys and am praying that you have some suggestion or maybe even a solution. Thanks in advance.