3.4 running rich

So ever since I replaced my 3.4 with a JDM engine it’s been running rich, and is slow to start. When I start it up I’m always on the starter for several seconds, like 3-5 seconds. It always starts, and runs fine, but it smells a little rich. Is there any practical way to tune this engine? All my research says no, or buy a supercharger, but I thought I’d ask anyway.

 

Older vehicles smell rich due to worn catalytic converters. It smells rich on startup because its supposed to be.

Only true way to tell if its rich is the fuel trim on a scanner.

 

I’m sure the CAT Is worn out, it never occurred to me that’s what could be making it smell rich.

Any ideas what might cause it to be slow to start? I definitely stay in the starter several seconds Longer than with the old engine (when it was running right)

 

A video of you starting it may help. Never timed mine but it seems like that's how long mine takes to fire each time? Unless it's below zero outside than it cranks a bit longer.