328 Cat questions

I'm putting the catalytic converter back on my 328. It's been in a box for a year, but I checked it before it went back on, and the matrix inside looked fine.

When I fired it up, the exhaust smelled "heavier" than before with the resonator, and when I turned it off a few minutes later, there was threads of smoke/exhaust/vapor(?) coming out of the exhaust for quite a while afterwards.

Is this normal? Does the cat need to burn back in after being unused for a year?