I use a pipe through my stock cat. With approx 45 degree bend at end of exhaust pointing down and no marks at all on the bar.
I wouldn't be suppose if your stock cat is hollow.
Thrash harder.
Don't ask silly questions like if spinning out can damage your car.
Spin it out and find out for yourself.
Where is the factory, maybe you can get some others to show you how it's done.
Good luck with it dude.
I'll give you my secret.
I use needle nose pliers to pull the fuses out. Using tools seperate us from the animals..
Simple things first. Electrical problem = check all fuses.
Clogged up from smoke seems unlikely.
The signal to the ecu comes from the cluster. If the cluster is working then that's good.
I would use an oscilloscope to see if the pin on the ecu is getting a signal and go from there. An auto electrician might be required depending on your skill level and equipment.
There's a huge difference between am auto and an r35 gearbox.
There no clutch, right, but ts not an auto.
I want to go fast. I don't crave a 'connection' to the car that an extra pedal gives you.
But I don't have enough money to go fast......