I have a cat back walker exhaust in my driveway. I'm trying to remove the stock exhaust. The big 2 into 1 flange has me stumped. The 15mm bolts are TIGHT. A breaker bar gets one of them moving, but the bolt head on the other side is spinning with no way to put a wrench on it! The "bolt head" has spikes on it so a socket won't go on. WTF? Ideas?

 

If by spikes you mean it looks like a torx bolt then you need to buy the proper wrench.
The other way is to get out the blue tip wrench, cut them off and then use regular bolts.

 

Not torx. They're spikes like thorns. Used a grinder and got em off. The service manual says not to reuse the studs anyway.