Anyone knows pls help!

[Hoang Nam Nhat]

I have problem with my 92-SR20 (Bluebird SSS, Japanese model) and need help.
I bought it recently, 50.000 miles, engines runs fine, no hesitation, good
idle except when deaccelerating it sometimes becomes irregular. I found this
can be fixed by adjusting the idle screw but the idle itself become higher
then. The "Check Engine Light" is On but goes off immediately after starting.
The real problem is that black smoke comes out at high rpm, fuel comsumption
is abnormally high (17-20 liters/100 km, twice as normal). I have replaced the
fuel filter, oil and oil filter, air filter, washed ignition wires, cleaned
the throat body, checked MAF (Hitachi, 4-pin; pin 1/GND: ~5V, pin 2/GND: 12V,
pin 3: grounded, pin 4/GND:~1.5V) and re-grounded it, checked TPS output
(3-pin, pin 1/GND ~5V, pin 2/3: varies from 1.2 to 5V). I have also checked
around the fuel line to see if there is any leak, but a friend says there will
not be fault in fuel system since it will result in low presure and difficult
starting problems. It now appears to me that the only problem is the
"possible" mal-function or mis-replacement of fuel injectors, but I dont know
how to check it, even if there are the original ones. Thank to anybody can
advice. Nam. PS: Can the injectors cause such terrible fuel consumption?