How am I getting a Slow Down light?!?

Bad vesicovini box (temp thermocouple ecu). If it has no temp ECUs.. then whatever they did is ****ing up. Simple as that. Look under the engine panels...

 

01 360 Spider

.. happened to me too.. intermittent problem. I bit the bullet and, not knowing which was bad, replaced both thermocouple ECUS (signal data converters) and no more slow down light.

Dunno about the aftermarket cat mod but sounds like your ECUs are missing a signal.

 

I also had the ECU/box thing go bad. Developed a crack at one plug-end. Dealer replaced free of charge as I had bought the car second hand from them.

I can leave the car sitting a week and it starts up just fine, you would have to have a failing battery if it required the trickle charger every night just to run fine the next day. I believe some have mentioned their car firing up just fine even if it sits a few weeks.

 

Same here. I have left my car sitting in the garage for a few days with no problems. Perhaps a good time to change the battery to a lighter one for weight savings.

 

Not if your battery is decent.

 

Unlikely. Catalyst ECUs issues and bad thermocouplers are a common problem. I replaced at least two catalyst ECUs during my 10 year ownership of my 355. There are plenty of threads here on how to diagnose both components and determine which is defective. You should own an OBDII scan tool. Ebay has them for cheap. I have a ELM 327 scan tool with Bluetooth connection to my IPhone. I downloaded an free app for my IPhone. Works great. Cost all of $10 or so. Scanning codes can assist with narrowing which side is bad....then by swapping components left to right you can see if the problem moves.