need a exh that is under 90db @75 ft undrer WOT
 

I have read the searched files, but I have a unigue issue.I am currently replacing my entire exhaust system. I have ready to install, KOOK's headers with cats. I need to choose a cat back that will keep my car under 90db@75ft under WOT. That is the rules at the 2 of the autox areas I race at. My car is a H/C car with a mild 224/224/116 cam. The current system of SLP LT's with cats, An ATR catback needed a 18in dynomax bullet mufflet added to make sound. I want to loose the bullet as it can rub my driveshaft so I need a catback that can flow for a 400rwhp na/ 490 rwho n2o car
thanks

I am currently in Germany where they are allowing us 95 Db @ 3' and 1/2 redline. My car is putting out slightly more power than yours. I am running Kooks LT's w.3.5 collectors and the merging them down to 3". No cats back to a Borla catback. The lowest it goes with all of that is 98.8 Db. Obviously, that is much closer than 75' though. Maybe you can check yours at this level to see where you are at.

Something that I have seen work is the cones from Dynatech (I think). They just slip into your tubing and lower your Db. I have seen one lower it as much as 4 Db. Summit sells them. However, that was on a mustang. Mine seems to react differently though. For some reason I put 1 in and my Db rose another poiint. I added another and it finally dropped to just below where I started. This probably isn't helping alot, but it is my experience.

Let me know if you find anything.

I tried the cones too and found that they did nothing for the sound.

I don't know exactly what db my magnaflow catback is, but it is not loud at all.