I recently modded my apexi world sport with 2.5" piping from the header back and now everytime i get on it, it makes this ringing noise up in the higher rpm's.

What could be causing this ?

I asked the muffler shop and they told me that its the straight through piping compared to apexi's 2.36" piping and the removal of a resonator thats making the noise. But before all t his the exhaust was perfect, it was just a little too quiet so i decided to up the size in diameter for the piping.

If anybody knows any info on why this happening to the exhaust please let me know.

The ringing noise is annoying and embarrasing to have when your pushing the car up into vtec.

 

I've got the same problem on my 92, i got a 2.5 inch custom system put in from the header back to the muffler, and now it buzzes....i hate it....shoulda just stayed with the quieter exhaust before. I'm really curious why it's doing this too.

 

Maybe the exhaust is bumping into the heat insulating metal. You know the thin razor sharp stuff that's under there. Just a thought.

I had a similar problem with a custom 3" cat back with a Thermal muffler, but took it out and went back to NA before I had a chance to solve it.