Aside from octane issues, what causes noise under heavy load?

[squid]

Dont want to be to negative but my experience is that a noise that gets worse under heavy load or brake load is one of three things if not detonation. 1. Main or rod bearings 2. Broken piston ring 3. Wristpin
If you have heard detonation before you should be able to tell if yours is different. Deep noises under load can be a sign of bearing trouble.

Hope its not though!