99 f150 catalytic converter removal
 

I have a 99 F150 with 5.4 that keeps blowing out driver side exahust manifold gasket, truck also throws service engine light with an o2 sensor on the left side. I have a partailly restricted catalytic converter. I don;t want to put or replace the cats on this old truck if I don;t have to, I live in a state that does not require inspections. Has anyone had any luck removing these and what improvements or problems did it cause? I know I will still have the service engine light on. mostly wondering about gas mileage and how the truck will run over all
Thanks in advance for any information you can provide