550 Stebro Center Pipe causing CHECK ENGINE light

Has anyone put a replacement center pipe on any Ferrari, particularly a 456 or 550; And had problems with engine sensors?
Yesterday, a local shop installed a Stebro center pipe on my 550. Afterwards, when I drove off, the "SLOW DOWN" warning light came on, blinking. But after a few blocks, the warning message went out. I then assumed that during installation (which included tack welding of the stainless steel) the Catalytic convertor thermocouples had become over-heated and that this was causing the warning light to indicate a possible heat-related problem. I drove home on the highway and noticed increased perforance and no additional sound: The perfect combination!

Once home, I telephoned FoDenver and Josh in service said to just keep an eye on the warning lamps.

Well, tonight, as soon as I started the engine, the CHECK ENGINE light came on, blinking amber. Due to distractions at the house, I had to let the car idle tonight for about 10 minutes before driving off.
Once on the highway, the center console CHECK ENGINE light continued to blink in amber. Then it went out. But the small CHECK ENGINE light on the right of the nacelle continued to be lit.

Then, after I stopped at a couple of places (each of which I shut the car off for minutes) the CHECK ENGINE light in the center went to blinking red and finally to continuous red, along with the small CHECK ENGINE light on the right of the cluster staying on. I immediately drove home and parked it.

As you can see in the attached photo, the Stebro pipes are smaller and much lighter than the OEM unit. But I'm wondering if the Stebro's smaller RESONATOR section has increased exhaust back pressure in the engine to some unacceptable level, or it is somehow causing the Cats to heat up too much.

My ultimate concern is that if the central CHECK ENGINE light stays on-- in continuous red-- whether I can drive the car to FoDenver for diagnosis... or if I have to Uninstall the Stebro, put the OEM unit back on, THEN drive it to Denver and reinstall it for diagnosis. That would be a total of $1,000 for a failed experiment! Ouch!

The Stebros make the car run quieter and NOTICIBLY FASTER, but I'm definately sensing increased heat coming up through the shifter gate, as though the Cats are hotter than normal.

I'd appreciate any input from anyone on their experience with aftermarket center pipes on a 550 or 456 (or any similar experiences with sensors and possible damage, because of aftermarket exhaust on any Ferrari model.)
Thanks, as always!
John
(attached photo)

I know that problem, my lights went on sometimes's, in my case i got two original Ferrari Cat's empty without cat's, just the covers, so that the police can't find anything during checking, because i drove without catalistic converters.
Actually i got the chance to buy the two cats in ebay for 200 hundred bucks, i add two new O2 sensors and now with cat's the light's never appear again.

I guess if you change anything on the exhaust system you will run into problems, in my chase i have also a stainless steal exhaust system mounted on my 94' Mondial t.

Have fun

Marcus from Germany

Thank you for your posting Marcus. Today, I have found that the CHECK ENGINE light is amber-- not red (I was probably "seeing red" last night at the thought of having caused thousands of dollars in damage!)

I hope that, like you, my problem is only a new sensor. I'm worried mostly by how HOT the 550 was running the first day we istalled the Stebros. Monday, I will talk with Ferrari of Denver and probably take it in for diagnostics in the next week or two, after I get new tires and allignment.
Thanks again! John

Dan at Stebro emailed me that I'm "the first" to have these problems. He's a great guy and I believe him. FoDenver thinks the problem is either O2 sensors or multivariate value computations by the ECU that are showing "Check Engine" (MV's are algorythms that compare incoming gas ratios to exhaust and then the ECU does a lookup for tolerances). Anyway, the car is running better than ever, it's quiet and I recommend that 550 owners consider the Stebro pipes, but get them installed by a real F-dealer who can do diagnosis...not at the local cowboy auto shop!