my 91 na backfires when i shift at high rpms. i thought the clogged cat was the cause but now have high flow bonez, rb headers, apexi dual n1 and still having the issue.

 

What is your question? Are you asking if backfires are detonation?

If so, they're not the same thing at all. Backfires happen when you let off the throttle quickly, and unburnt gas ignites in the exhaust system. You can check your dashpot on the TB to see if it is adjusted correctly. It slowly closes the throttle plates when you let off. Backfires are common under these conditions. It's usually with catless exhaust systems, but it can still happen with a cat in place.