Ok so removing the stock cat...

IDZRVIT

Demon bolts 0 - IDZRVIT 2!!! I just came up from my garage after spending 2 hours getting those two bastirds out. I put PB blaster on the right side bolt - waste of time as the oil can't penetrate. How do I know? There was no penetrating oil on the threads when I removed it. I used a 1/2" drive 6 pt impact socket attached to a 6" extension attached to a universal attached to couple of other extensions. Put a 24" pipe over the 1/2" bar and applied torque. Success. The left side was the same method without the universal and I removed the air box. Sheared the head of the bolt clean off. Success. The key to get those bolts out is to make 100% sure that the socket is square onto the bolt head. If not, you'll round the head of the bolt. There isn't any trick to get these out such as using heat and penetrating oil and ??? Quality tools and a strong forearm is all that is required.

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"America.... still builds rockets!"
Vette: 355 cid, 400 rwhp
'13 CTS-V Coupe: 6.2L LSA, 556HP