There's supposed to be a gasket there. So yes

 

So would that solve my really bad emissions problem? Would it most likely pass now? Or should I put a new cat on?

 

Can't say for sure.
It would not hurt to check your ignition parts. It's free to inspect

 

Ok so I have the header fixed and it doesn't leak anymore, o put in a new o2 sensor with a new catalytic converter. I have to take my car in to try inspection again. I was hoping to take it in tomorrow. I have driven around 200 miles with the repairs. Is this enough miles that I can take it in for emissions now? The catalytic converter smells kind of like burnt plastic. That is normal right?

 

How long did you drive the car before having the emissions tested?

For a sniff test car I use to do a 30 minute loop keeping the RPM's up and accessories off. I would also keep the engine at about 1500-2000 rpm's while waiting. This helps keep the catalytic converter warm so it will burn hydrocarbons.

 

200 miles

 

Drive the car at least 20-30 miles making sure it is at operating temp and everything is warm. This will be the most efficient for the engine.

What O2 sensor did you go with? Stick with NTK or Denso.

 

if it doesn't pass run the car down to like 1/4 tank and put half can of coleman camping fuel in, drive it around on highway for a while and try again