There comes a time when fuel injector cleaner just won't get the job done. If your injectors are old then you might want to by a new set and upgrade them while you are at it. When they don't atomize the fuel enough during high load you'll get incomplete combustion. Hey.., you can always try taking one of those small bullet vibrators, set on high, and place it at the top of the injector, (against the fuel rail) for a few minutes while the car is idling. It might dislodge what is blocking your injectors.
It ain't ultrasonic cleaning but it might be close enough. You'd have to do it at idle though to keep the pressure in the rail high. Or disconnect the vacuum line from the regulator, plug it and then idle up slowly to near 2500 and see if it clears up.