detonation in third only?

[mark '87 930]

I hear what seems to be detonation at WOT.. but only in 3rd gear. I recently took a long voyage with the car and was able to record some LM-1 time. All seems ok in the AFR region, but 3 gear for some reason sounds like it's not good. I don''t get it in 2nd or 4th (mind you, 4th at 4000+RPM is not easy to measure on public roads..) so I wonder if it could be transmission related.. but it really sounds like engine. thoughts?

[MikeD930]

I think it would also detonate in 4th gear. Load on the engine is higher in 3rd and 4th gear. I'd back down the boost. Be careful not to detonate again!

[A930Rocket]

Don't try to keep re-creating the detonation! Damage can occur very quickly. Verify your AF on a dyno in 3rd gear starting at 2500-3000 rpms.