car wont start ...just head a head gasket replacement and valve job from malibu on 2000 Chevrolet Malibu

no waterin oil car drove fine for a week and then one day it wouldnt go over 2500 rpm or 40 mph until eventually it wouldnt even start

Asked by for the 2000 Chevrolet Malibu
Work needs to be re-checked. Shop did the work? JUST headgaskets ? heads pressure tested? Original cause and symptoms of headgasket failure ? Overheating due to clogged converter?.........does it even matter at this point ?
check converter undo the oxygen sensor from the catalytic converter the one closest to the engine try to undo both before catalytic converter and if it starts they or blocked also check fuel pressure
........never mind.