Hey Scotty, I've changed everything fuel pump, spark plugs, boots, ignition control module, ignition coil, fuel filter, fuel injector prongs, air filter. This thing doesn't want to go and the check engine light is flashing it doesnt have power and I eating gas cause the misfire I suppose.I only got misfiring code p300. Now its saying major vacuum leak code 400 and something all these weeks later Any ideas?

It could be the battery. If the battery is old enough, it could still power the car, but not have enough power.

The battery is less than a year old but just in case I charged it to full and took less than 30 minutes

Huh? I didn't see what model or reference to it. I remmy back then when one of the repair tech I used to work with over 20 years ago was working on car with red hot cat converter. Took him two days but don't remmy what it was.. however, I remmy he mentioned that the cat was hot to begin with because it was running to rich for it.

Bad knock sensor or O2 sensors possibly. If its detecting a bad engine knock it could go into "limp mode".. If the knock sensor is bad and its detecting a knock that isn't there, same thing could happen. If it's running rich I'd check the O2 sensors and Mass Air Flow sensor to see if they need to be replaced/cleaned. If the cat is glowing it may have fried one if not both of the O2 sensors. Check all those and check out Scotty's video about how to easily find a vacuum leak with a cigar

Its a 2004 alero 2.2 liter