430 Scuderia exhaust valve bypass

That is correctly plumbed. It has to have a port to atmosphere to work properly.

 

That wasn't a kit but it was common to be done before the Forza kit came out. this likely has a spare sport switch located in place of the blanking plug just left of steering wheel. I have seen a lot of these cars have boosters fail and it seams to be most prevalent on a hard and quick brake application after a hard acceleration. I you have a hard pedal when stepping on the brakes in those conditions let up very slightly on the pedal pressure, if the assist comes back its a booster. Check for brake fluid in the booster when you disassemble it. It happens enough on the 430 and the 360 that we keep a booster and master cylinder in stock at the shop.

 

Your car likely had a recall for the master cylinder brake cap. We have found some with brake fluid in them and it only takes a few ounces to ruin the booster. Interesting I have never replaced one a second time on a car yet. We had been installing an aftermarket brake reservoir cap for years and it looks like Ferrari is doing the same now under the recall.
The other area to check is to ensure the check valve to the booster is in good shape. A bad check valve can cause a similar issue.

 

It will need a booster. Not a cap. I have replaced a few of them now and the difference is significant. Personally.. that cap thing is B.S. there are hundreds of thousands of cars that use the EXACT same cap as Ferrari does and there has NEVER been an issue.

 

These days its far better to control these things entirely in software. You can now tailor the exhaust valve opening times and % of throttle pedal opening specifically for each different driving mode.

This is very nice as it requires no extra parts to fail. For instance in race mode you can have it open aggressively above 2% throttle (like the 599 GTO does) and in normal closed most of the time. etc. then you can just switch mode to quiet or liven up the driving. In fact I've also done this for other models than the Scud including the 575M, 612 etc. These can also be paired with different performance modes so you get big differences in 'attitude' and performance between the modes. Makes the car so much more enjoyable and no electronic aftermarket parts to go wrong in the future or retrofit.