replaced OEM catalytic converter with Magnaflow catalytic converter, upstream one

I have already replaced the downstream OEM catalytic converter months ago with the Magnaflow one.
This weekend, I replaced the upstream OEM catalytic converter with a Magnaflow one. I'm not in California so it wasn't a problem ordering one online and installing it myself.
I tried to remove a broken bolt that is in the engine for one of the exhaust manifold bolts. That was not successful. I tried using a torch and I tried using an extraction tool and I tried using the torch with the extraction tool. I ended up cutting it down because I couldn't get it out.
The Magnaflow one is a lot lighter than the OEM one.
As for flow, I don't know if it is more free flowing but the opening in the lower flange is a bit larger than the OEM one.
The upper bolts were welded on and did not align with the exhaust manifold. I had to bend two bolts slightly with a hammer to get the bolts to go through the exhaust manifold.
The bracket holding the cat to the engine didn't fit the same way it did before. The holes aligned but the distance isn't right. I had to use washers to get the bracket pushed out.
There are two stubs welded on to hold the O2 wire holderss for the downstream O2 sensor wires, those were good.
The bottom flange is not threaded like on the OEM one. I had to get new nuts and bolts for that.

It's been over a week now with the new catalytic converter. It drives like it did awhile back. I can step on it and the revs start climbing.
Before I replaced the cat, when I mashed the pedal, the tach would go up very slowly unless I was going downhill.
I'm pretty sure, without doing a pressure test, that the old cat was clogged which caused the exhaust manifold-to-cat gasket to blow out.
I'm kind of wishing I just installed a header and moved the downstream sensor after the second cat into a new bung. At least it is environmentally safe. They don't check emissions where I live.