Petrol staying on

How about your catalytic converter...sounds clogged, need to confirm, and replace...

hi mate, from what you are saying here indicates that theres a recorded fault in the ecu, and there for needs to be put on a diagnotic unit to locate the said problems

I'm guessing petrol is the US equivalent to gasoline so you either have a problem with the gauge or the sensor that sends fuel level info to the gauge which is located in the gas tank.

I would first renew the petrol tank cap, or the gasket on it, if you can obtain one. Then see if the fault is cured. It is very common for a worn cap to cause the engine check light to glow, on any make.
To reset the ECU this procedure is said to work, although I think it is very weird. It would not seem to be damaging though
http://www.alfaowner.com/Forum/alfa-147-156-and-gt/201163-ecu-reset-its-a-miracle-cure.html

PETROL LIGHT ON MEAN EITHER FUEL GETTING LOW OR FUEL LINES COULD BE STOPPED UP.

you need new blinker fluid

you havent put diesel in by mistake ,have a sniif at the filler cap

most likely the sender in the gas tank is bad.

If your sure the tank is above the last 2 gallons the sensor is most likely bad. You should have the sensor replaced. It is part of the same system that detects fuel level.

IS THE RED LIGHT THAT IS STAYING ON THE BATTERY LIGHT? IF SO IT COULD BE AN ELECTRICAL FAULT, AND IS NOT FIRING UP THE ELECTRIC FUEL PUMP