It seems to me that your engine is running lean. Normally, the mixture is controlled by the ECU so that mixture is almost normal (lambda = 1).

If the mixture is lean, and the O2 sensor still works, you can measure the voltage of the O2 sensor (connector is on the firewall, right side, green wire). Connect a digital voltmeter this connector (+ terminal), the - terminal to ground. When the mixture is lean, the voltage is below 500 mV (0 to 250 mV). When its high (600 - 800mV), the mixture is rich. With a normal working engine, the signal is travelling between lean and rich, with a cycle time from about 0.5 to 1 sekond.

If your mixture is lean, the reason can be : fuel injectors, pressure regulator, AMM. Most suspicious to me is the AMM (had the same problem years ago).

You can fool the AMM, so that the mixture will be richer :

Take it out the car, take away the inlet screen, inside you see a little tube with the hot wire in it. Don't touch it !. Make an obstruction between the innertube and the outer (some foam will work). Mount it again.

Now, the engine will run richer, because the AMM thinks there is going more air through it (only the inner tube is measuring !).

It worked fine for me (now for 4 years).

Good luck.