2003 Toyota Solara converter question

Hello. I have a 2003 Toyota Solara 2.4 with 205,000 miles on it. I recently took it in to have it inspected and the mechanic found the exhaust system had weakened due to rust around the flex pipe, on the front tube of the exhaust system.

I had the mechanic replace the part with OEM materials. The problem is they had problems removing one of the studs from the exhaust manifold. They worked on it for a long time by spraying it with lubes, heating it red hot with a torch (repeatedly), etc. Finally they had to cut the stud off and drill a hole to bolt the new front tube in.

Now that the new system is bolted in place, I get dizzy and headachy when driving the car. At first it smelled really bad, because the front pipe also has a second converter. I don't really notice the smell anymore, but I still get the symptoms.

I had them recheck the system for leaks and they say there aren't any. I also washed the engine down to eliminate any remnants of spray lube that may be left under there.

Do you think they could have damaged the front catalytic converter (in the exhaust manifold) by heating the flange too much or by getting spray lube in there?

I have been through two tanks of gas and still seem to have the problem. Note that my symptoms are also symptoms of anxiety so maybe I'm just worrying too much. :)

Also, what is the smell that comes from a new catalytic converter and is it harmful?