On my 01 Ranger the Studs that once held the manifolds and cat. Converter became super coroded to the point were the other night the Cat. Converter separated from the manifolds. I'm know I will need to replace the Studs the only prob3lome is I can't get the old ones out. On one of them I sprayed it with pb, wated a while, and pounded it with a hammer for 20 minutes and made close to zero progress. What would be some suggestions for quicker ways to remove these.

 

If there is still something left off the stud, you can take to a muffler shop.
For a small charge they will get it out.
They probably use and acetylene/oxy torch.

I've gotten the most stubborn nuts/bolts out with that method.

If the stud is so far gone, you can use a counter clock wise drill and drill and tap it out, but drilling it down the centre and tapping isn't the easiest and best way, that's for sure.

Some times in these cases, I just drill and tap over size with new threads.

 

Yes, take it to an independent exhaust shop if you can find one, lol.
They will get nuts off lickity split, and have replacements in stock

That is all exhaust guys do all day long, remove rusted corroded studs, nuts and bolts.
They have ways and tools to get it done fast

My favorite is "wax", heat up the stud and nut and then press a candle onto the threads, wax will be sucked up into the rusted area, then impact drive to bring stud or nut out

Google: stuck bolts and wax

 

It's the heat that does it Ron, not so much the wax.
The heat, like phosphoric acid chemically changes the rust and turns it black, it breaks the bond.
Phosphoric acid would work if you could get it to penetrate past the rust on the surface, but in the case of rusted bolts and studs it won't work.

I find it takes an oxy/acetylene torch to do the job.
The area has to be heated to at least cherry red, some times more.
Those little MPS hand held gas torches at the hardware store don't cut the mustard.

The mistake that most do when they do heat it up to cherry red is they try and remove the nut/stud while it's still hot.
This doesn't work because even though the rust seal has broken, the metal is expanded and is vey tight.
All that has to be done is just to get it moving at this point.

It has to be allowed to cool down so when you spray penetrating oil on it, the oil just doesn't evaporate. (or the wax if you like)
At this point it's easy to work the penetrating oil into the threads now that the steel has shrunk back to normal.

Once fully cooled I've removed studs and nuts with my bare hand, the trick is to let it cool down.

One has to be carful when working with cast iron, the whole area has to be heated evenly concentrating on the stud area .
If too much heat is applied to quickly in one area, the casting can crack.
You don't want to quench it water either, the sudden drop in temperature can crack it too.