Getting Too Much GAS??

1980 280ZX was running fine until it seems like it is getting too much or not enough gas. It's hard to keep running and only goes about 30mph with very stinky exhaust. We decided to clean the fuel injectors with a pressurized can of Echilin from Napa so we unplugged the fuel pump, pinched off the fuel return line and ran it on the can of injector cleaner. Funny thing was that it seemed to run better on the injector cleaner than on gas, but only ran for a few minutes on the can of injector cleaner and it was gone and an unusual amount of white smoke was coming out of the exhaust. When I had used this kind of pressurized cleaner in the past the cars ran for 10-15 minutes, so we have come to the conclusion that it's getting too much gas? We already tried a fuel pressure regulator from another 280Z parts car.

Any Suggestions??

When the ignition is on, the pump is always running? Is that normal?